EP2224462A2 - Niobpulver, Sinter davon und Kondensator damit - Google Patents

Niobpulver, Sinter davon und Kondensator damit Download PDF

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Publication number
EP2224462A2
EP2224462A2 EP10003487A EP10003487A EP2224462A2 EP 2224462 A2 EP2224462 A2 EP 2224462A2 EP 10003487 A EP10003487 A EP 10003487A EP 10003487 A EP10003487 A EP 10003487A EP 2224462 A2 EP2224462 A2 EP 2224462A2
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Prior art keywords
niobium
niobium powder
powder
sintered body
capacitor
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EP10003487A
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English (en)
French (fr)
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EP2224462B1 (de
EP2224462A3 (de
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Kazuhiro Omori
Kazumi Naito
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Resonac Holdings Corp
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Showa Denko KK
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004—Details
    • H01G9/04—Electrodes or formation of dielectric layers thereon
    • H01G9/042—Electrodes or formation of dielectric layers thereon characterised by the material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004—Details
    • H01G9/04—Electrodes or formation of dielectric layers thereon
    • H01G9/048—Electrodes or formation of dielectric layers thereon characterised by their structure
    • H01G9/052—Sintered electrodes
    • H01G9/0525—Powder therefor
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/045—Alloys based on refractory metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004—Details
    • H01G9/022—Electrolytes; Absorbents
    • H01G9/025—Solid electrolytes
    • H01G9/028—Organic semiconducting electrolytes, e.g. TCNQ
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

  • the present invention relates to a niobium powder with a large capacitance per unit mass and good leakage current characteristics, a sintered body using the above-mentioned niobium powder, and a capacitor using the above-mentioned sintered body.
  • Capacitors for use in electronic apparatus such as portable telephones and personal computers are required to be small in size and large in capacitance.
  • a tantalum capacitor is preferably used, because the capacitance is large, not in proportion to the size, and the tantalum capacitor also has good characteristics.
  • the tantalum capacitor usually employs a sintered body of a tantalum powder as an anode. In order to increase the capacitance of the tantalum capacitor, it is necessary to increase the mass of the sintered body, or to use a sintered body having an increased surface area obtained by pulverizing the tantalum powder.
  • the increase in mass of the sintered body inevitably enlarges the shape, so that the requirement for a small-sized capacitor is not satisfied.
  • the tantalum powder is finely pulverized to increase the specific surface area, the pore size in the tantalum sintered body decreases, and the number of closed pores increases during the sintering step. The result is that the sintered body cannot be easily impregnated with a cathode agent in the subsequent step.
  • One approach to solve these problems is a capacitor using a sintered body of a powder material which has a greater dielectric constant than the tantalum powder.
  • One powder material which has such a greater dielectric constant is a niobium powder.
  • Japanese Laid-Open Patent Application No. 55-157226 discloses a method for producing a sintered element for a capacitor. This method comprises the steps of subjecting a niobium powder ranging from an agglomerate to fine particles with a particle diameter of 2.0 ⁇ m or less to pressure molding and sintering, finely cutting the molded sintered body, connecting a lead portion to the finely cut particles of the sintered body, and thereafter sintering the connected body.
  • a niobium powder ranging from an agglomerate to fine particles with a particle diameter of 2.0 ⁇ m or less to pressure molding and sintering, finely cutting the molded sintered body, connecting a lead portion to the finely cut particles of the sintered body, and thereafter sintering the connected body.
  • United States Patent No. 4, 084, 965 discloses a capacitor using a sintered body of a niobium powder with a particle size of 5.1 ⁇ m obtained from a niobium ingot through hydrogenation and pulverizing.
  • the capacitor disclosed has, however, a high leakage current value (hereinafter referred to as an LC value), and therefore the serviceability is poor.
  • the LC value is improved by partially nitriding a niobium powder.
  • the LC value of the obtained capacitor may become exceptionally high.
  • United States Patent No. 6, 051, 044 discloses a niobium powder which has a particular BET specific surface area and contains nitrogen in a particular amount. A method for decreasing the leakage current is also disclosed. However, there is no disclosure nor suggestion concerning a niobium powder containing another element which can form an alloy with niobium. Furthermore, this patent does not disclose nor suggest the heat resistance necessary for capacitors in soldering and the like or stability of LC value against thermal history.
  • An object of the present invention is to provide a niobium powder capable of providing a capacitor having good heat resistance with a large capacitance per unit mass and a small leakage current value, a sintered body using the above-mentioned niobium powder, and a capacitor using the above-mentioned sintered body.
  • the inventors of the present invention have found that a low LC value and good heat resistance can be maintained even in a capacitor provided with a large capacitance by decreasing the particle diameter of a niobium powder when at least one element selected from various elements which can form an alloy with niobium is added to niobium.
  • the present invention has thus been accomplished.
  • the present invention basically provides a niobium powder of the below (1) to (29), a sintered body of (30) to (31) obtained by sintering the niobium powders, a capacitor of (32) to (42), a process for producing niobium powders of (43) to (46), an electronic circuit of (47) and an electronic instrument of (48).
  • alloy in the present application includes a solid solution with the other alloy components.
  • ppm and “%” in the present application mean “ppm by mass” and “% by mass” respectively unless explained otherwise.
  • the capacitor of the present invention which has a large capacitance and good leakage current characteristics, niobium powder and sintered body thereof which attribute to those good capacitor characteristics will be explained with regard to the following four groups ((1) ⁇ (4)):
  • the first group of the present invention relates to a niobium powder and a sintered body thereof, wherein the niobium powder contains at least one element selected from the transition elements of group 6 in the periodic table, that is, chromium, molybdenum, and tungsten.
  • Chromium, molybdenum, and tungsten are elements that can form an alloy with niobium.
  • the most effective for lowering the leakage current value is tungsten, while molybdenum and chromium follow in that order. It is therefore most preferable that the niobium powder of the first group of the present invention contains tungsten.
  • Such a tungsten-containing niobium powder may further comprise molybdenum and/or chromium, preferably chromium.
  • the total amount of these elements may be 10 mol% or less, preferably in the range of 0.01 mol% to 10 mol%, more preferably in the range of 0.1 mol% to 7 mol% in the niobium powder.
  • a sintered body of a niobium powder for a capacitor with the niobium powder containing at least one element selected from the group consisting of chromium, molybdenum, and tungsten in an amount of 10 mol% or less, more preferably in the range of 0:01 mol% to 10 mol% of the niobium powder.
  • the content of the above-mentioned element is less than 0.01 mol%, it is impossible to inhibit the tendency whereby oxygen in a dielectric film formed by electrolytic oxidation, to be described later, is apt to diffuse into the niobium metal side. Consequently, the stability of a film obtained by electrolytic oxidation, i.e., dielectric film, cannot be maintained, so that the LC value cannot be effectively lowered. If the content of the above-mentioned element is more than 10mol%, the amount of niobium itself in the niobium powder decreases. As a result, the capacitance of the capacitor decreases.
  • the most preferable amount of at least one element selected from the group consisting of chromium, molybdenum, and tungsten is in the range of 0.01 to 10 mol%.
  • the above-mentioned element be contained in an amount of 3 mol% or less, and more preferably in the range of 0.05 to 3 mol% in the niobium powder.
  • the niobium powder have a mean particle size (mean particle diameter) of 5 ⁇ m or less, and more preferably 4 ⁇ m, or less to increase the specific surface area of the powder.
  • the mean particle diameter of the niobium powder of the present invention may be 0.2 ⁇ m or more and 5 ⁇ m or less. The reason for this is as follows.
  • the capacitance of the capacitor can be increased merely by increasing the specific surface area.
  • the niobium powder has a spherical shape
  • the smaller the particle diameter of the niobium powder the larger the capacitance of the obtained capacitor.
  • the niobium powder is not in a completely spherical shape, and occasionally contains flake-shaped particles.
  • the characteristics required for the capacitor of the present invention are not only a large capacitance but also good leakage current properties. This cannot be achieved simply by enlarging the specific surface area of the powder.
  • a niobium powder containing at least one element selected from the group consisting of chromium, molybdenum, and tungsten as a raw material to produce a sintered body, it becomes possible to provide a capacitor capable of satisfying both the above-mentioned capacitor characteristics, and a niobium sintered body that can provide such capacitor characteristics.
  • TABLE 1 shows the particle diameter and the specific surface area of respective tungsten-containing niobium powders which the inventors of the present invention prepared through pulverizing as one embodiment.
  • the mean particle size herein used is a value D 50 , which represents a particle diameter, measured using a particle size distribution measuring apparatus "Microtrac” (trademark), made by Microtrac Corporation, when the mass percentage reaches 50% by cumulative distribution by mass.
  • the specific surface area is a value measured by the BET method.
  • the mean particle size of the niobium powder containing at least one element selected from the group consisting of chromium, molybdenum, and tungsten is less than 0.05 ⁇ m
  • a sintered body made from the niobium powder has a small pore size and has many closed pores. Therefore, there is a tendency for the sintered body to be not easily impregnated with an agent for cathode as described later. The result is that the capacitance of the obtained capacitor cannot be increased, and therefore, the above-mentioned sintered body is not suitable for capacitors.
  • the mean particle size exceeds 5 ⁇ m a large capacitance cannot be obtained.
  • a large capacitance can be obtained in the present invention by employing a niobium powder preferably having a mean particle size of 0.05 ⁇ m or more and 5 ⁇ m or less.
  • the niobium powder of the present invention have a BET specific surface area of at least 0.5 m 2 /g, more preferably at least 1.0m 2 /g, and further preferably at least 2.0 m 2 /g.
  • the niobium powder of the present invention be a powder with a BET specific surface area of 0.5 to 40 m 2 /g, more preferably 1 to 20 m 2 /g, and particularly preferably 1 to 10 m 2 /g.
  • the dielectric constant ( ⁇ ) of niobium is about two times greater than that of tantalum.
  • chromium, molybdenum, or tungsten is a valve metal that is one of the capacitor characteristics. Therefore it has not been known that the dielectric constant ⁇ of the niobium powder containing at least one element selected from the group consisting of chromium, molybdenum, and tungsten will increase.
  • the niobium powder containing at least one element selected from the group consisting of chromium, molybdenum, and tungsten is controlled to have a small mean particle size and is made into a sintered body with a large capacitance, as mentioned above, there is no peculiar increase in the LC value.
  • the present invention will now be described by taking tungsten as an example of the transition elements of the group 6 in the periodic table.
  • the present invention is not limited to this example, but also applies to the case where chromium or molybdenum is used.
  • the tungsten-containing niobium powder used to prepare a sintered body have a mean particle size of 0.2 ⁇ m or more and 5 ⁇ m or less as mentioned above.
  • the tungsten-containing niobium powder having such a mean particle size can be prepared from, for example, a hydride of a niobium - tungsten alloy in the form of an ingot, pellet, or powder through pulverizing and dehydrogenation.
  • a niobium powder prepared by subjecting a hydride of a niobium ingot, pellet, or powder to pulverizing and dehydrogenation, or by pulverizing a sodium reduced form of potassium fluoroniobate is mixed with tungsten carbide, tungsten oxide, or tungsten powder.
  • a mixture of niobium oxide and tungsten oxide may be subj ected to carbon reduction.
  • a tungsten-containing niobium powder with a desired mean particle size can be obtained by adjusting the content of hydride in the niobium - tungsten alloy, and the pulverizing time and a pulverizer.
  • a niobium powder with a mean particle size of from 0.2 ⁇ m or more to 5 ⁇ m or less may be added to the tungsten-containing niobium powder thus obtained.
  • the niobium powder to be added can be prepared, for example, by pulverizing a sodium reduced form of potassium fluoroniobate, or subjecting a hydride of a niobium ingot to pulverizing and dehydrogenation, or by subjecting niobium oxide to carbon reduction.
  • the tungsten-containing niobium powder may be partially bonded to at least one of nitrogen, carbon, boron, or sulfur.
  • Any of the tungsten-containing niobium nitride, tungsten-containing niobium carbide, tungsten-containing niobium boride, and tungsten-containing niobium sulfide, resulting from the bonding to nitrogen, carbon, boron, and sulfur, respectively may be added alone, or the two to four kinds may be selectively contained.
  • the amount of element for bonding may be more than 0 ppm and not more than 200,000 ppm, preferably in the range of 50 ppm to 100,000 ppm, and more preferably 200 ppm to 20,000 ppm when the tungsten-containing niobium powder has a mean particle size from 0.05 ⁇ m to 5 ⁇ m.
  • the capacitance characteristics deteriorate to such an extent that the niobium powder becomes unsuitable for a capacitor.
  • Nitridation of the tungsten-containing niobium powder can be performed by any of liquid nitridation, ion nitridation, or gas nitridation, or by a combination of those methods.
  • Gas nitridation under a nitrogen gas atmosphere is preferred because the system can be made simple and the operation can be made easy.
  • the tungsten-containing niobium powder may be allowed to stand under a nitrogen gas atmosphere.
  • the tungsten-containing niobium powder partially nitrided to a desired extent can be obtained at a nitriding atmosphere temperature of 2000°C or less within one hundred hours.
  • An increase in processing temperature can curtail the processing time.
  • the tungsten-containing niobium powder can be carbonized by any method of gas carbonization, solid-phase carbonization, or liquid carbonization.
  • the tungsten-containing niobium powder may be allowed to stand together with a carbon source of a carbon-containing organic material such as a carbon material or methane at 2000°C or less under reduced pressure for one minute to one hundred hours.
  • the tungsten-containing niobium powder can be borided by gas boronization or solid-phase boronization.
  • the tungsten-containing niobium powder may be allowed to stand together with a boron source such as boron pellets or boron halide, i.e., trifluoroboron under reduced pressure at temperatures of 2000°C or less for one minute to one hundred hours.
  • a boron source such as boron pellets or boron halide, i.e., trifluoroboron under reduced pressure at temperatures of 2000°C or less for one minute to one hundred hours.
  • the tungsten-containing niobium powder can be sulfided by any of gas sulfidation, ion sulfidation, or solid-phase sulfidation.
  • gas sulfidation under a sulfur gas atmosphere
  • the tungsten-containing niobium powder may be allowed to stand under a sulfur atmosphere.
  • the tungsten-containing niobium powder sulfided to a desired extent can be obtained at temperatures of 2000°C or less and a standing time of one hundred hours or less. The higher the processing temperature, the shorter the processing time.
  • the tungsten-containing niobium powder can be used for a capacitor after granulation to have a desired configuration.
  • the granulated powder may be mixed with a proper amount of ungranulated niobium powder after granulation.
  • the tungsten-containing niobium powder not subjected to granulation is allowed to stand under high vacuum, heated to an appropriate temperature, and then subjected to cracking.
  • the tungsten-containing niobium powder not subjected to granulation is mixed with an appropriate binder such as camphor, polyacrylic acid, poly (methyl acrylate), or poly (vinyl alcohol), and a solvent such as acetone, alcohol, acetate, or water, and thereafter the resulting mixture is subjected to cracking.
  • the tungsten-containing niobium powder thus granulated can improve pressure-moldability in the preparation of a sintered body.
  • the granulated powder it is preferable that the granulated powder have a mean particle size of 10 ⁇ m to 500 ⁇ m.
  • the mean particle size of the granulated powder is 10 ⁇ m or less, partial blocking takes place, which degrade the flowability toward a mold.
  • the granulated powder has a mean particle size of 500 ⁇ m or more, an angular portion of a molded article is easily chipped off after pressure molding.
  • Granulated powders have preferably a mean particle size of 30 ⁇ m to 250 ⁇ m, and particularly preferably of 60 ⁇ m to 250 ⁇ m because the sintered body is easily impregnated with a negative electrode material after pressure molding of the niobium powder in the production of a capacitor.
  • nitridation, carbonization, boronization, and sulfidation can be carried out, not only for the niobium powder, but also for the granulated niobium powder and for the niobium sintered body.
  • the tungsten-containing niobium sintered body for a capacitor according to the present invention is produced by sintering the aforementioned tungsten-containing niobium powder or the granulated tungsten-containing niobium powder.
  • An example of a method for producing the sintered body will be described later, but does not limit the present invention.
  • a tungsten-containing niobium powder is subjected to pressure molding to have a predetermined shape, and the molded material is heated at 500°C to 2000°C, preferably 900°C to 1500°C, and more preferably 900°C to 1300°C under the application of a pressure of 10 -5 to 10 2 Pa (pascal) for one minute to ten hours.
  • niobium powder comprising at least one element selected from the group consisting of boron, aluminum, gallium, indium and thallium is used as a starting material of the niobium powder.
  • the boron, aluminum, gallium, indium and thallium for use in the present invention are elements capable of forming an alloy with niobium and among these, boron and aluminum have an effect of most reducing the leakage current and next effective are gallium, indium and thallium in this order. Accordingly, in the present invention, boron or aluminum is particularly preferably incorporated into the niobium powder.
  • the boron-containing niobium powder may further contain aluminum, gallium, indium and thallium.
  • the total content of these elements in the niobium powder is 10 mol% or less, preferably from 0.01 to 10 mol% and more preferably from 0.1 to 7 mol%.
  • the niobium powder formed into a sintered body and used for a capacitor in the present invention preferably contains at least one element selected from the group consisting of boron, aluminum, gallium, indium and thallium, in the range of 10 mol% or less, more preferably from 0.01 to 10 mol% and particularly preferably 0.1 to 7mol%.
  • the content of the element is less than 0.01 mol%, oxygen in the dielectric film formed by the electrolytic oxidation which is described later cannot be inhibited from diffusing toward the internal niobium metal side, as a result, the stability of the electrolytic oxide film (the dielectric film) cannot be maintained and the effect of reducing LC can be hardly obtained.
  • the content of the element exceeds 10 mol%, the content of the niobium itself in the niobium powder is reduced, as a result, the capacitance as a capacitor decreases.
  • the content of at least one element selected from the group consisting of the boron, aluminum, gallium, indium and thallium is preferably from 0.01 to 10 mol%.
  • the content of the element in the niobium powder is preferably 7 mol% or less, more preferably from 0.10 to 7 mol%.
  • the niobium powder of the present invention preferably has a mean particle size of 5 ⁇ m or less, more preferably 4 ⁇ m or less. Also, the mean particle size of the niobium powder of the present invention is preferably from 0.05 to 4 ⁇ m. The reasons therefor are described above with regard to the niobium powder of the first group.
  • the starting material niobium powder used for manufacturing a sintered body is a niobium powder comprising at least one element selected from the group consisting of boron, aluminum, gallium, indium and thallium, whereby a capacitor satisfying both of the above-described properties or a niobium sintered body capable of ensuring those capacitor properties can be provided.
  • the mean particle size (D 50 , ⁇ m) and the specific surface area (S, m 2 /g) of a boron-containing niobium powder manufactured as one example by the present inventors (produced by a pulverization method) are shown in Table 2 below.
  • TABLE 2 Mean Particle Size Specific Surface (D 50 ) Area (S) ( ⁇ m) (m 2 /g) 5.0 0.60 2.0 1.3 0.9 2.4 0.5 4.3 0.2 10.0 0.1 20.9 0.05 39.2
  • the mean particle size (D 50 ; ⁇ m) shown in Table 2 above is a value measured using a particle size distribution measuring apparatus ("Microtrac", trade name, manufactured by Microtrac Company) (the D 50 value indicates a particle size when the cumulative % by mass corresponds to 50% by mass).
  • the specific surface area is a value measured by the BET method.
  • the mean particle size of the niobium powder comprising at least one element selected from the group consisting of boron, aluminum, gallium, indium and thallium exceeds 5 ⁇ m, a capacitor having a large capacitance cannot be obtained, whereas if the mean particle size is less than 0.05 ⁇ m, the pore size becomes small and closed pores increase when a sintered body is produced from the powder, therefore, a cathode material which is described later cannot be easily impregnated, as a result, the niobium powder cannot provide a capacitor having a large capacitance and the sintered body thereof is not suitable for use in a capacitor.
  • the niobium powder for use in the present invention preferably has a mean particle size of 0.05 to 4 ⁇ m, whereby a large-capacitance capacitor can be obtained.
  • the niobium powder of the present invention is preferably a powder having a BET specific surface area of at least 0.5 m 2 /g, more preferably at least 1 m 2 /g, and still more preferably at least 2 m 2 /g. Also, the niobium powder of the present invention preferably has a BET specific surface area of 0.5 to 40 m 2 /g, more preferably from 1 to 20 m 2 /g and particularly preferably from 1 to 10 m 2 /g.
  • niobium With respect to the dielectric constant ( ⁇ ), niobium is known to have a dielectric constant as large as about two times the dielectric constant of tantalum, however, whether or not boron, gallium, indium and thallium are a valve metal having capacitor properties is not known.
  • Aluminum is a valve acting metal but the dielectric constant thereof is known to be smaller than that of niobium. Accordingly, even when at least one element selected from the group consisting of boron, aluminum, gallium, indium and thallium is incorporated into niobium, it is not known whether ⁇ of the niobium powder containing the element increases.
  • the LC value is not peculiarly increased insofar as at least one element of boron, aluminum, gallium, indium and thallium is contained.
  • Niobium has a high bonding strength to an oxygen element as compared with tantalum and therefore, oxygen in the electrolytic oxide film (dielectric material film) is liable to diffuse toward the internal niobium metal side, however, in the sintered body of the present invention, a part of niobium is bonded to at least one element of boron, aluminum, gallium, indium and thallium and therefore, oxygen in the electrolytic oxide film is not easily bonded to the internal niobium metal and inhibited from diffusing toward the metal side, as a result, the stability of the electrolytic oxide film can be maintained and an effect of reducing the LC value and the dispersion thereof even in the case of a capacitor having a fine particle size and a high capacitance can be attained.
  • a boron-containing niobium power for use in the manufacture of a sintered body preferably has a mean particle size of 0.05 to 4 ⁇ m as described above.
  • the boron-containing niobium powder having such a mean particle size can be obtained, for example, by a method of pulverizing and dehydrogenating a hydride of a niobium-boron alloy ingot, pellet or powder.
  • the boron-containing niobium powder can also be obtained by a method of mixing boric acid, boron oxide and boron powder with a niobium powder formed by pulverizing and dehydrogenating a hydride of a niobium ingot, pellet or powder, by pulverizing a sodium reduction product of potassium fluoroniobate or by pulverizing a reduction product resulting from reducing a niobium oxide using at least one member of hydrogen, carbon, magnesium, aluminum, or by a method of carbon-reducing a mixture of niobium oxide and boron oxide.
  • a boron-containing niobium powder having a desired mean particle size can be obtained by controlling the amount of the niobium-boron alloy ingot hydrogenated, the pulverization time, the grinding machine or the like.
  • the thus-obtained boron-containing niobium powder may be mixed with a niobium powder having a mean particle size of 5 ⁇ m or less to adjust the boron content.
  • the niobium powder added here may be obtained, for example, by a method of pulverizing a sodium reduction product of potassium fluoroniobate, a method of pulverizing and dehydrogenating a hydroxide of a niobium ingot, a method of reducing a niobium oxide using at least one member of hydrogen, carbon, magnesium and aluminum, or a method of hydrogen-reducing a niobium halide.
  • a part of the boron-containing niobium powder may be surface-treated by nitridation, carbonization, sulfidation and further boronization.
  • the powder may comprise any of these products obtained by the surface-treatment of nitridation, carbonization, sulfidation or boronization, more specifically, the powder may comprise any of boron-containing niobium nitride, boron-containing niobium carbide, boron-containing niobium sulfide and boron-containing niobium boride.
  • the powder may also comprise two, three or four of these products in combination.
  • the sum total of the bonding amounts that is, the total content of nitrogen, carbon, boron and sulfur varies depending on the shape of the boron-containing niobium powder, however, in the case of a powder having a mean particle size of approximately from 0.05 to 5 ⁇ m, the total content is more than 0 ppm and not more than 200,000 ppm, preferably from 50 to 200,000 ppm, more preferably from 200 to 20,000 ppm. If the total content exceeds 200,000 ppm, the capacitance characteristics are deteriorated and the fabricated product is not suitable as a capacitor.
  • the nitridation of the boron-containing niobium powder can be performed by any one of liquid nitridation, ion nitridation and gas nitridation or by a combination thereof.
  • gas nitridation in a nitrogen gas atmosphere is preferred because the apparatus therefor is simple and the operation is easy.
  • the gas nitridation in a nitrogen gas atmosphere can be attained by allowing the above-described boron-containing niobium powder to stand in a nitrogen gas atmosphere. With an atmosphere temperature of 2,000°C or less and a standing time of one hundred hours or less, a boron-containing niobium powder having an objective nitrided amount can be obtained. The treatment time can be shortened by performing this treatment at a higher temperature.
  • the carbonization of the boron-containing niobium powder may be any one of gas carbonization, solid-phase carbonization and liquid carbonization.
  • the boron-containing niobium powder may be carbonized by allowing it to stand together with a carbon material or a carbon source such as an organic material having carbon (e.g., methane), at 2,000°C or less under reduced pressure for one minute to one hundred hours.
  • a carbon material or a carbon source such as an organic material having carbon (e.g., methane)
  • the sulfidation of the boron-containing niobium powder may be any one of gas sulfidation, ion sulfidation and solid-phase sulfidation.
  • the gas sulfidation in a sulfur gas atmosphere can be attained by allowing the boron-containing niobium powder to stand in a sulfur atmosphere. With an atmosphere temperature of 2,000°C or less and a standing time of one hundred hours or less, a boron-containing niobium powder having an objective sulfudized amount can be obtained.
  • the treatment time can be shortened by performing the treatment at a higher temperature.
  • the boronization of the boron-containing niobium powder may be either gas boronization or solid-phase boronization.
  • the boron-containing niobium powder may be boronized by allowing it to stand together with a boron source such as boron pellet or boron halide (e.g., trifluoroboron), at 2,000°C or less for one minute to one hundred hours under reduced pressure.
  • a boron source such as boron pellet or boron halide (e.g., trifluoroboron)
  • the boron-containing niobium powder for capacitors of the present invention may be used after granulating the boron-containing niobium powder into an appropriate shape or may be used by mixing an appropriate amount of non-granulated niobium powder after the above-described granulation.
  • Examples of the granulation method include a method where non-granulated boron-containing niobium powder is allowed to stand in a high vacuum, heated to an appropriate temperature and then cracked, and a method where non-granulated boron-containing niobium powder is mixed with an appropriate binder such as camphor, polyacrylic acid, polymethyl acrylic acid ester or polyvinyl alcohol, and a solvent such as acetone, alcohols, acetic acid esters or water, and then cracked.
  • an appropriate binder such as camphor, polyacrylic acid, polymethyl acrylic acid ester or polyvinyl alcohol
  • a solvent such as acetone, alcohols, acetic acid esters or water
  • the boron-containing niobium powder granulated as such is improved in the press-molding property at the production of a sintered body.
  • the mean particle size of the granulated powder is preferably from 10 to 500 ⁇ m. If the mean particle size of the granulated powder is less than 10 ⁇ m, partial blocking takes place and the fluidity into a metal mold deteriorates, whereas if it exceeds 500 ⁇ m, the molded article after the press-molding is readily broken at the corner parts.
  • the mean particle size of the granulated powder is more preferably from 30 to 250 ⁇ m because a cathode agent can be easily impregnated at the manufacture of a capacitor after sintering the press-molded article.
  • the boron-containing niobium sintered body for capacitors of the present invention is produced by sintering the above-described boron-containing niobium powder or granulated boron-containing niobium powder.
  • the production method for the sintered body is not particularly limited, however, the sintered body may be obtained, for example, by press-molding the boron-containing niobium powder into a predetermined shape and then heating it at 500 to 2,000°C, preferably from 900 to 1,500°C, more preferably from 900 to 1,300°C, for one minute to ten hours under a pressure of 10 -5 to 10 2 Pa.
  • a niobium powder comprising at least one element selected from the group consisting of cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic and bismuth can used as a starting material of the niobium powder.
  • the cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic and bismuth are elements capable of forming an alloy with niobium.
  • a niobium powder comprising at least one element selected from the group consisting of rhenium, neodymium, zinc, arsenic, phosphorus, germanium and tin is preferred, and a niobium powder comprising at least one element selected from the group consisting of rhenium, neodymium and zinc is more preferred.
  • the niobium powder is, for example, a rhenium-containing niobium powder comprising at least one element of cerium, neodymium, titanium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic and bismuth.
  • the total content of these elements in the niobium powder is 10 mol% or less, preferably from 0.01 to 10 mol%, more preferably from 0.1 to 7 mol%.
  • the total content of the element is less than 0.01 mol%, oxygen in the dielectric film formed by the electrolytic oxidation which is described later cannot be inhibited from diffusing toward the niobium metal side, as a result, the stability of the electrolytic oxide film (the dielectric film) cannot be maintained and the effect of reducing LC can be hardly obtained.
  • the total content of the element exceeds 10 mol%, the content of the niobium itself in the niobium powder is reduced, as a result, the capacitance as a capacitor decreases.
  • the total content of at least one element selected from the group consisting of cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic and bismuth is preferably from 0.01 to 10 mol%.
  • the content of the element in the niobium powder is preferably 7 mol% or less, more preferably from 0.1 to 7 mol%.
  • the niobium powder of the present invention preferably has a mean particle size of 5 ⁇ m or less, more preferably 4 ⁇ m or less. Also, the mean particle size of the niobium powder is preferably from 0.05 to 4 ⁇ m. The reasons therefor are described above with regard to the niobium powder of the first group.
  • the starting material niobium powder used for manufacturing a sintered body is a niobium powder comprising at least one element selected from the group consisting of cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic and bismuth, whereby a capacitor satisfying both of the above-described properties or a niobium sintered body capable of ensuring those capacitor properties can be provided.
  • the mean particle size (D 50 , ⁇ m) and the specific surface area (S, m 2 /g) of a rhenium-containing niobium powder manufactured as one example by the present inventors (produced by a pulverization method) are shown in Table 3 below.
  • Table 3 Mean Particle Size Specific Surface (D 50 ) Area (S) ( ⁇ m) (m 2 /g) 4.9 0.63 2.0 1.3 0.9 2.6 0.5 4.9 0.2 11.0 0.1 20.7 0.05 38.4
  • the mean particle size (D 50 ; ⁇ m) shown in Table 3 is a value measured using a particle size distribution measuring apparatus ("Microtrac", trade name, manufactured by Microtrac Company) (the D 50 value indicates a particle size when the cumulative % by mass corresponds to 50% by mass).
  • the specific surface area is a value measured by the BET method.
  • the mean particle size of the niobium powder comprising at least one element selected from the group consisting of cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic and bismuth exceeds 5 ⁇ m, a capacitor having a large capacitance cannot be obtained, whereas if the mean particle size is less than 0.05 ⁇ m, the pore size becomes small and closed pores increase when a sintered body is produced from the powder, therefore, a cathode material which is described later cannot be easily impregnated, as a result, the niobium powder cannot provide a capacitor having a large capacitance and the sintered body thereof is not suitable for use in a capacitor.
  • the niobium powder for use in the present invention preferably has a mean particle size of 0.05 to 5 ⁇ m, whereby a large-capacitance capacitor can be obtained.
  • the niobium powder of the present invention is preferably a powder having a BET specific surface area of at least 0.5 m 2 /g, more preferably at least 1 m 2 /g, and still more preferably at least 2 m 2 /g. Also, the niobium powder of the present invention preferably has a BET specific surface area of 0.5 to 40 m 2 /g, more preferably from 1 to 20 m 2 /g and particularly preferably from 1 to 10 m 2 /g.
  • niobium With respect to the dielectric constant ( ⁇ ), niobium is known to have a dielectric constant as large as about two times the dielectric constant of tantalum, however, whether cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic and bismuth are a valve metal having capacitor properties is not known.
  • the LC value is not peculiarly increased insofar as at least one element of cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic and bismuth is contained.
  • Niobium has a high bonding strength to an oxygen element as compared with tantalum and therefore, oxygen in the electrolytic oxide film (dielectric material film) is liable to diffuse toward the internal niobium metal side, however, in the sintered body of the present invention, a part of niobium is bonded to at least one element of cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic and bismuth and therefore, oxygen in the electrolytic oxide film is not easily bonded to the internal niobium metal and inhibited from diffusing toward the metal side, as a result, the stability of the electrolytic oxide film can be maintained and an effect of reducing the LC value and the dispersion thereof even in the case of a capacitor having a fine particle size and a high capacitance can be attained.
  • the present invention is described below mainly using rhenium as an example, however, the present invention is not limited thereto and the following contents are applied also to the cases using at least one element selected from the group consisting of cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic and bismuth.
  • the rhenium-containing niobium power for use in the manufacture of a sintered body preferably has a mean particle size of 0.05 to 4 ⁇ m as described above.
  • the rhenium-containing niobium powder having such a mean particle size can be obtained, for example, by a method of pulverizing and dehydrogenating a hydride of niobium-rhenium alloy ingot, pellet or powder.
  • the rhenium-containing niobium powder can also be.obtained by a method of mixing rhenium powder or an oxide, sulfide, sulfate, halide salt, nitrate, organic acid salt or complex salt of rhenium with a niobium powder formed by pulverizing and dehydrogenating a hydride of niobium ingot, pellet or powder, by pulverizing a sodium reduction product of potassium fluoroniobate or by pulverizing a reduction product of niobium oxide reduced using at least one member of hydrogen, carbon, magnesium, aluminum and the like; or by a method of magnesium-reducing a mixture of niobium oxide and rhenium oxide.
  • the niobium powder containing rhenium, zinc and germanium can be obtained, for example, by a method of pulverizing and dehydrogenating a hydride of niobium-rhenium-zinc-germanium alloy ingot, pellet or powder.
  • This niobium powder can also be obtained by a method of mixing rhenium powder, zinc powder and germanium powder, or oxides, sulfides, sulfates, halide salts, nitrates or organic acid salts of rhenium, zinc, germanium with a niobium powder formed by pulverizing and dehydrogenating a hydride of niobium ingot, pellet or powder; by pulverizing a sodium reduction product of potassium fluoroniobate or by pulverizing a reduction product of niobium oxide reduced using at least one member of hydrogen, carbon, magnesium, aluminum and the like; or by a method of magnesium-reducing a mixture of niobium oxide, rhenium oxide, zinc oxide and germanium oxide.
  • a rhenium-containing niobium powder having a desired mean particle size can be obtained by controlling the amount of the niobium-rhenium alloy hydrogenated, the pulverization time, the grinding machine or the like.
  • the thus-obtained rhenium-containing niobium powder may be mixed with a niobium powder having a mean particle size of 5 ⁇ m or less to adjust the rhenium content.
  • the niobium powder added here may be obtained, for example, by a method of pulverizing a sodium reduction product of potassium fluoroniobate, a method of pulverizing and dehydrogenating a hydride of niobium ingot, a method of reducing a niobium oxide using at least one member of hydrogen, carbon, magnesium and aluminum, or a method of hydrogen-reducing a niobium halide.
  • a part of the rhenium-containing niobium powder may be surface-treated by nitridation, boronization, carbonization or sulfidation.
  • Any of the rhenium-containing niobium nitride, rhenium-containing niobium boride, rhenium-containing niobium carbide and rhenium-containing niobium sulfide, obtained by the surface-treatment using nitridation, boronization, carbonization or sulfidation, may be contained or two, three or four thereof may also be contained in combination.
  • the amount bonded thereof that is, the total content of nitrogen, boron, carbon and sulfur varies depending on the shape of the rhenium-containing niobium powder, however, in the case of powder having a mean particle size of approximately from 0.05 to 5 ⁇ m, the total content is more than 0 ppm and not more than 200, 000 ppm, preferably from 50 to 100,000 ppm, particularly preferably from 200 to 20,000 ppm. If the total content exceeds 200,000 ppm, the capacitance properties are deteriorated and the fabricated product is not suitable as a capacitor.
  • the nitridation of the rhenium-containing niobium powder can be performed by any one of liquid nitridation, ion nitridation and gas nitridation or by a combination thereof.
  • gas nitridation in a nitrogen gas atmosphere is preferred because the apparatus therefor is simple and the operation is easy.
  • the gas nitridation in a nitrogen gas atmosphere can be attained by allowing the above-described rhenium-containing niobium powder to stand in a nitrogen gas atmosphere. With an atmosphere temperature of 2,000°C or less and a standing time of one hundred hours or less, a rhenium-containing niobium powder having an objective nitrided amount can be obtained. The treatment time can be shortened by performing this treatment at a higher temperature.
  • the boronization of the rhenium-containing niobium powder may be either gas boronization or solid-phase boronization.
  • the rhenium-containing niobium powder may be boronized by allowing a boron-containing niobium powder to stand together with a boron source such as boron pellet or boron halide (e.g., trifluoroboron), at 2,000°C or less forgone minute to one hundred hours under reduced pressure.
  • a boron source such as boron pellet or boron halide (e.g., trifluoroboron)
  • the carbonization of the rhenium-containing niobium powder may be any one of gas carbonization, solid-phase carbonization and liquid carbonization.
  • the rhenium-containing niobium powder may be carbonized by allowing it to stand together with a carbon source such as a carbon material or an organic material having carbon (e.g., methane), at 2,000°C or less for one minute to one hundred hours under reduced pressure.
  • a carbon source such as a carbon material or an organic material having carbon (e.g., methane)
  • the sulfidation of the rhenium-containing niobium powder may be any one of gas sulfidation, ion sulfidation and solid-phase sulfidation.
  • the gas sulfidation in a sulfur gas atmosphere can be attained by allowing the rhenium-containing niobium powder to stand in a sulfur atmosphere. With an atmosphere temperature of 2,000°C or less and a standing time of one hundred hours or less, a rhenium-containing niobium powder having an objective sulfudized amount can be obtained.
  • the treatment time can be shortened by performing the treatment at a higher temperature.
  • the rhenium-containing niobium powder for capacitors of the present invention may be used after granulating the rhenium-containing niobium powder into an appropriate shape or may be used by mixing an appropriate amount of non-granulated niobium powder after the above-described granulation.
  • Examples of the granulation method include a method where non-granulated rhenium-containing niobium powder is allowed to stand in a high vacuum and heated to an appropriate temperature and then the mixture is cracked, and a method where non-granulated or granulated rhenium-containing niobium powder is mixed with an appropriate binder such as camphor, polyacrylic acid, polymethyl acrylic acid ester or polyvinyl alcohol, and a solvent such as acetone, alcohols, acetic acid esters or water, and then the mixture is cracked.
  • an appropriate binder such as camphor, polyacrylic acid, polymethyl acrylic acid ester or polyvinyl alcohol, and a solvent such as acetone, alcohols, acetic acid esters or water
  • the rhenium-containing niobium powder granulated as such is improved in the press-molding property at the production of a sintered body.
  • the mean particle size of the granulated powder is preferably from 10 to 500 ⁇ m. If the mean particle size of the granulated powder is less than 10 ⁇ m, partial blocking takes place and the fluidity into a metal mold deteriorates, whereas if it exceeds 500 ⁇ m, the molded article after the press-molding is readily broken at the corner parts.
  • the mean particle size of the granulated powder is more preferably from 30 to 250 ⁇ m because a cathode agent can be easily impregnated at the manufacture of a capacitor after sintering the press-molded article.
  • the rhenium-containing niobium sintered body for capacitors of the present invention is produced by sintering the above-described rhenium-containing niobium powder or granulated rhenium-containing niobium powder.
  • the production method for the sintered body is not particularly limited, however, the sintered body may be obtained, for example, by press-molding the rhenium-containing niobium powder into a predetermined shape and then heating it at 500 to 2,000°C, preferably from 900 to 1,500°C, more preferably from 900 to 1,300°C, for one minute for one hundred hours under a pressure of 10 -5 to 10 2 Pa (pascal).
  • a niobium powder comprising at least one element selected from the group consisting of rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, selenium and tellurium can used as a starting material of the niobium powder capable of satisfying the capacitor properties.
  • the rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, sulfur, selenium and tellurium are elements capable of forming an alloy with niobium.
  • a niobium powder comprising at least one element selected from the group consisting of lanthanum, yttrium, erbium, ytterbium and lutetium is preferred, and a niobium powder comprising at least one element selected from the group consisting of lanthanum and yttrium is more preferred.
  • the niobium powder is, for example, a lanthanum-containing niobium powder comprising at least one element of rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, sulfur, selenium and tellurium.
  • the total content of these elements in the niobium powder is 10 mol% or less, preferably from 0.01 to 10 mol%, more preferably from 0.1 to 7 mol%.
  • the total content of the element is less than 0.01 mol%, oxygen in the dielectric film formed by the electrolytic oxidation which is described later cannot be inhibited from diffusing toward the niobium metal side, as a result, the stability of the electrolytic oxide film (the dielectric film) cannot be maintained and the effect of reducing LC can be hardly obtained.
  • the total content of the element exceeds 10 mol%, the content of the niobium itself in the niobium powder is reduced, as a result, the capacitance as a capacitor decreases.
  • the total content of at least one element selected from the group consisting of rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, sulfur, selenium and tellurium is preferably from 0.01 to 10 mol%.
  • the content of the element in the niobium powder is preferably 7 mol% or less, more preferably from 0.1 to 7 mol%.
  • the niobium powder of the present invention preferably has a mean particle size of 5 ⁇ m or less, more preferably 4 ⁇ m or less. Also, the mean particle size of the niobium powder is preferably from 0.05 to 4 ⁇ m. The reasons therefor are described above with regard to the niobium powder of the first group.
  • the starting material niobium used for manufacturing a sintered body is a niobium powder comprising at least one element selected from the group consisting of rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, selenium and tellurium, whereby a capacitor satisfying both of the above-described properties or a niobium sintered body capable of ensuring those capacitor properties can be provided.
  • the mean particle size (D 50 , ⁇ m) and the specific surface area (S, m 2 /g) of a lanthanum-containing niobium powder manufactured as one example by the present inventors (all produced by a pulverization method) are shown in Table 4 below.
  • Table 4 Mean Particle Size Specific Surface (D 50 ) Area (S) ( ⁇ m) (m 2 /g) 5.1 0.61 1.9 1.4 0.9 2.5 0.5 5.1 0.2 11.1 0.1 20.8 0.05 38.7
  • the mean particle size (D 50 ; ⁇ m) shown in Table 4 is a value measured using a particle size distribution measuring apparatus ("Microtrac", trade name, manufactured by Microtrac Company) (the D 50 value indicates a particle size when the cumulative % by mass corresponds to 50% by mass)
  • the specific surface area is a value measured by the BET method.
  • the mean particle size of the niobium powder comprising at least one element selected from the group consisting of rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, selenium and tellurium exceeds 5 ⁇ m, a capacitor having a large capacitance cannot be obtained, whereas if the mean particle size is less than 0.05 ⁇ m, the pore size becomes small and closed pores increase when a sintered body is produced from the powder, therefore, a cathode material which is described later cannot be easily impregnated, as a result, the niobium powder cannot provide a capacitor having
  • the niobium powder for use in the present invention preferably has a mean particle size of 0. 05 to 5 ⁇ m, whereby a large-capacitance capacitor can be obtained.
  • the niobium powder of the present invention is preferably a powder having a BET specific surface area of at least 0.5 m 2 /g, more preferably at least 1 m 2 /g, and still more preferably at least 2 m 2 /g. Also, the niobium powder of the present invention preferably has a BET specific surface area of 0.5 to 40 m 2 /g, more preferably from 1 to 20 m 2 /g, and particularly preferably from 1 to 10 m 2 /g.
  • niobium is known to have a dielectric constant as large as about two times the dielectric constant of tantalum, however, whether rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, selenium and tellurium are a valve metal having capacitor properties is not known.
  • the LC value is not peculiarly increased insofar as at least one element of rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, selenium and tellurium is contained.
  • Niobium has a high bonding strength to an oxygen element as compared with tantalum and therefore, oxygen in the electrolytic oxide film (dielectric material film) is liable to diffuse toward the internal niobium metal side, however, in the sintered body of the present invention, a part of niobium is bonded to at least one element of rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, selenium and tellurium and therefore, oxygen in the electrolytic oxide film is not easily bonded to the internal niobium metal and inhibited from diffusing toward the metal side, as a result,
  • the present invention is described below mainly using lanthanum as an example, however, the present invention is not limited thereto and the following contents are applied also to the cases using rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, selenium and tellurium.
  • the lanthanum-containing niobium power for use in the manufacture of a sintered body preferably has a mean particle size of 0.05 to 4 ⁇ m as described above.
  • the lanthanum-containing niobium powder having such a mean particle size can be obtained, for example, by a method of pulverizing and dehydrogenating a hydride of niobium-lanthanum alloy ingot, pellet or powder.
  • the lanthanum-containing niobium powder can also be obtained by a method of mixing lanthanum powder or a hydride, oxide, sulfide, sulfate, halide salt, nitrate, organic acid salt or complex salt of lanthanum with a niobium powder formed by pulverizing and dehydrogenating a hydride of niobium ingot, pellet or powder, by pulverizing a sodium reduction product of potassium fluoroniobate or by pulverizing a reduction product of niobium oxide reduced using at least one member of hydrogen, carbon, magnesium, aluminum and the like; or by a method of magnesium-reducing a mixture of niobium oxide and lanthanum oxide.
  • the niobium powder containing lanthanum, hafnium and iridium can be obtained, for example, by a method of pulverizing and dehydrogenating a hydride of niobium-lanthanum-hafnium-iridium alloy ingot, pellet or powder.
  • This niobium powder can also be obtained by a method of mixing lanthanum powder, hafnium powder and iridium powder, or hydrides, oxides, sulfides, sulfates, halide salts, nitrates or organic acid salts of lanthanum, hafnium and iridium with a niobium powder formed by pulverizing and dehydrogenating a hydride of niobium ingot, pellet or powder, by pulverizing a sodium reduction product of potassium fluoroniobate or by pulverizing a reduction product of niobium oxide reduced using at least one member of hydrogen, carbon, magnesium, aluminum and the like; or by a method of magnesium-reducing a mixture of niobium oxide, lanthanum oxide, hafnium oxide and iridium oxide.
  • a lanthanum-containing niobium powder having a desired mean particle size can be obtained by controlling then amount of the niobium-lanthanum alloy hydrogenated, the pulverization time, the grinding machine or the like.
  • the contents of tantalum and metal element other than the elements described above namely, rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, selenium and tellurium) each is 1,000 ppm or less and the oxygen content is from 3,000 to 60,000 ppm.
  • niobium powder containing the element described above namely, at least one element selected from the group consisting of rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, selenium and tellurium).
  • the element described above namely, at least one element selected from the group consisting of rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,
  • the thus-obtained lanthanum-containing niobium powder may be mixed with a niobium powder having a mean particle size of 5 ⁇ m or less to adjust the lanthanum content.
  • the niobium powder added here may be obtained, for example, by a method of pulverizing a sodium reduction product of potassium fluoroniobate, a method of pulverizing and dehydrogenating a hydride of niobium ingot, a method of reducing a niobium oxide using at least one member of hydrogen, carbon, magnesium and aluminum, or a method of hydrogen-reducing a niobium halide.
  • the lanthanum-containing niobium powder for capacitors of the present invention may be used after granulating the lanthanum-containing niobium powder into an appropriate shape or may be used by mixing an appropriate amount of non-granulated niobium powder after the above-described granulation.
  • Examples of the granulation method include a method where non-granulated lanthanum-containing niobium powder is allowed to stand under highly reduced pressure, heated to an appropriate temperature and then the mixture is cracked, a method where non-granulated or granulated lanthanum-containing niobium powder is mixed with an appropriate binder such as camphor, polyacrylic acid, polymethyl acrylic acid ester or polyvinyl alcohol, and a solvent such as acetone, alcohols, acetic acid esters or water, and then the mixture is cracked, a method where non-granulated or granulated lanthanum-containing niobium powder is mixed with an appropriate binder such as camphor, polyacrylic acid, polymethyl acrylic acid ester or polyvinyl alcohol, and a solvent such as acetone, alcohols, acetic acid esters or water, the mixture is sintered under highly reduced pressure to vaporize and thereby remove the added binder and solvent through evaporation, sublimation or thermal decomposition and the sintered
  • the lanthanum-containing niobium powder granulated as such is improved in the press-molding property at the production of a sintered body.
  • the mean particle size of the granulated powder is preferably from 10 to 500 ⁇ m. If the mean particle size of the granulated powder is less than 10 ⁇ m, partial blocking takes place and the fluidity into a metal mold deteriorates, whereas if it exceeds 500 ⁇ m, the molded article after the press-molding is readily broken at the corner parts.
  • the mean particle size of the granulated powder is more preferably from 30 to 250 ⁇ m because a cathode agent can be easily impregnated at the manufacture of a capacitor after sintering the press-molded article.
  • the lanthanum-containing niobium sintered body for capacitors of the present invention is produced by sintering the above-described lanthanum-containing niobium powder or granulated lanthanum-containing niobium powder.
  • the production method for the sintered body is not particularly limited, however, the sintered body may be obtained, for example, by press-molding the lanthanum-containing niobium powder into a predetermined shape and then heating it at 500 to 2,000°C, preferably from 900 to 1,500°C, more preferably from 900 to 1,300°C, for one minute to ten hours under a pressure of 10 -5 to 10 2 Pa (pascal) .
  • a part of the lanthanum-containing niobium powder, granulated powder or sintered body may be subjected to nitridation, boronization, carbonization, sulfidation or a plurality of these treatments.
  • any of the obtained lanthanum-containing niobium nitride, lanthanum-containing niobium boride, lanthanum-containing niobium carbide and lanthanum-containing niobium sulfide may be contained or two or more thereof may also be contained in combination.
  • the amount bonded thereof that is, the total content of nitrogen, boron, carbon and sulfur varies depending on the shape of the lanthanum-containing niobium powder, however, the total content is more than 0 ppm and not more than 200, 000 ppm, preferably 50 to 100,000 ppm, more preferably from 200 to 20, 000 ppm. If the total content exceeds 200,000 ppm, the capacitance properties are deteriorated and the fabricated product is not suitable as a capacitor.
  • the nitridation of the lanthanum-containing niobium powder, granulated powder or sintered body can be performed by any one of liquid nitridation, ion nitridation and gas nitridation or by a combination thereof.
  • gas nitridation in a nitrogen gas atmosphere is preferred because the apparatus therefor is simple and the operation is easy.
  • the gas nitridation in a nitrogen gas atmosphere can be attained by allowing the above-described lanthanum-containing niobium powder, granulated powder or sintered body to stand in a nitrogen gas atmosphere.
  • a lanthanum-containing niobium powder, granulated powder or sintered body having an objective nitrided amount can be obtained.
  • the treatment time can be shortened by performing this treatment at a higher temperature.
  • the boronization of the lanthanum-containing niobium powder, granulated powder or sintered body may be either gas boronization or solid-phase boronization.
  • the lanthanum-containing niobium powder, granulated powder or sintered body may be boronized by allowing it to stand together with a boron source such as boron pellet or boron halide (e.g., trifluoroboron), at 2,000°C or less for approximately from 1 minute to 100 hours under reduced pressure.
  • a boron source such as boron pellet or boron halide (e.g., trifluoroboron)
  • the carbonization of the lanthanum-containing niobium powder, granulated powder or sintered body may be any one of gas carbonization, solid-phase carbonization and liquid carbonization.
  • the lanthanum-containing niobium powder, granulated powder or sintered body may be carbonized by allowing it to stand together with a carbon material or a carbon source such as an organic material having carbon (e.g., methane), at 2,000°C or less under reduced pressure for approximately from 1 minute to 100 hours.
  • the sulfidation of the lanthanum-containing niobium powder, granulated powder or sintered body may be any one of gas sulfidation, ion sulfidation and solid-phase sulfidation.
  • the gas sulfidation in a sulfur gas atmosphere can be attained by allowing the lanthanum-containing niobium powder, granulated powder or sintered body to stand in a sulfur atmosphere. With an atmosphere temperature of 2, 000°C or less and a standing time of 100 hours or less, a niobium powder, granulated powder or sintered body having an objective sulfudized amount can be obtained.
  • the treatment time can be shortened by performing the treatment at a higher temperature.
  • a lead wire comprising a valve-acting metal such as niobium or tantalum and having appropriate shape and length is prepared and this lead wire is integrally molded at the press-molding of the niobium powder such that a part of the lead wire is,inserted into the inside of the molded article, whereby the lead wire is designed to work out to a leading line of the sintered body.
  • a valve-acting metal such as niobium or tantalum
  • a capacitor can be manufactured by interposing a dielectric material between this one of the electrodes and the other electrode (counter electrode).
  • the dielectric material used here for the capacitor is preferably a dielectric material mainly comprising niobium oxide.
  • the dielectric material mainly comprising niobium oxide can be obtained, for example, by chemically forming the lanthanum-containing niobium sintered body as one part electrode in an electrolytic solution.
  • an aqueous protonic acid solution is generally used, such as aqueous 0.1% phosphoric acid solution or aqueous sulfuric acid solution, or 1% acetic acid solution or aqueous adipic acid solution.
  • the capacitor of the present invention is an electrolytic capacitor and the lanthanum-containing niobium electrode serves as an anode.
  • the other electrode (counter electrode) to the niobium sintered body is not particularly limited and, for example, at least one material (compound) selected from electrolytic solutions, organic semiconductors and inorganic semiconductors known in the art of aluminum electrolytic capacitor, may be used.
  • the electrolytic solution examples include a dimethylformamide-ethylene glycol mixed solution having dissolved therein 5% by mass of an isobutyltripropylammonium borotetrafluoride electrolyte, and a propylene carbonate-ethylene glycol mixed solution having dissolved therein 7% by mass of tetraethylammonium borotetrafluoride.
  • the organic semiconductor include an organic semiconductor comprising a benzenepyrroline tetramer and chloranile, an organic semiconductor mainly comprising tetrathiotetracene, an organic semiconductor mainly comprising tetracyanoquinodimethane, and an electrically conducting polymer comprising a repeating unit represented by formula (1) or (2): wherein R 1 to R 4 each independently represents a monovalent group selected from the group consisting of a hydrogen atom, a linear or branched, saturated or unsaturated alkyl, alkoxy or alkylester group having from 1 to 10 carbon atoms, a halogen atom, a nitro group, a cyano group, a primary, secondary or tertiary amino group, a CF 3 group, a phenyl group and a substituted phenyl group; each of the pairs R 1 and R 2 , and R 3 and R 4 may combine at an arbitrary position to form a divalent chain for forming at least one 3-, 4-,
  • R 1 to R 4 of formula (1) or (2) each independently preferably represents a hydrogen atom, a linear or branched, saturated or unsaturated alkyl or alkoxy group having from 1 to 6 carbon atoms, and each of the pairs R 1 and R 2 , and R 3 and R 4 may combine with each other to form a ring.
  • the electrically conducting polymer comprising a repeating unit represented by formula (1) above is preferably an electrically conducting polymer comprising a structure unit represented by the following formula (3) as a repeating unit: wherein R 6 and R 7 each independently represents a hydrogen atom, a linear or branched, saturated or unsaturated alkyl group having from 1 to 6 carbon atoms, or a substituent for forming at least one 5-, 6- or 7-membered saturated hydrocarbon cyclic structure containing two oxygen atoms resulting from the alkyl groups combining with each other at an arbitrary position; and the cyclic structure includes a structure having a vinylene bond which may be substituted, and a phenylene structure which may be substituted.
  • the electrically conducting polymer containing such a chemical structure is electrically charged and a dopant is doped thereto.
  • a dopant for the dopant, known dopants can be used without limitation.
  • the inorganic semiconductor include an inorganic semiconductor mainly comprising lead dioxide or manganese dioxide, and an inorganic semiconductor comprising triiron tetraoxide. These semiconductors may be used individually or in combination of two or more thereof.
  • Examples of the polymer containing a repeating unit represented by formula (1) or (2) include polyaniline, polyoxyphenylene, polyphenylene sulfide, polythiophene, polyfuran, polypyrrole, polymethylpyrrole, and substitution derivatives and copolymers thereof.
  • polyaniline polyoxyphenylene, polyphenylene sulfide, polythiophene, polyfuran, polypyrrole, polymethylpyrrole, and substitution derivatives and copolymers thereof.
  • polypyrrole, polythiophene and substitution derivatives thereof e.g., poly(3,4-ethylenedioxythiophene)).
  • the fabricated capacitor can have a smaller impedance value and can be more increased in the capacitance at a high frequency.
  • the electrically conducting polymer layer is produced, for example, by a method of polymerizing a polymerizable compound comprising aniline, thiophene, furan, pyrrole, methylpyrrole or a substitution derivative thereof under the action of an oxidizing agent capable of undergoing a satisfactory oxidation reaction of dehydrogenating double oxidation.
  • Examples of the polymerization reaction from the polymerizable compound (monomer) include vapor phase polymerization and solution polymerization.
  • the electrically conducting polymer layer is formed on the surface of the niobium sintered body having thereon a dielectric material.
  • the electrically conducting polymer is an organic solvent-soluble polymer capable of solution coating, a method of coating the polymer on the surface of the sintered body to form an electrically conducting polymer layer is used.
  • One preferred example of the production method using the solution polymerization is a method of dipping the niobium sintered body having formed thereon a dielectric layer in a solution containing an oxidizing agent (Solution 1) and subsequently dipping the sintered body in a solution containing a monomer and a dopant (Solution 2) to form an electrically conducting polymer on the surface of the sintered body.
  • the sintered body may be dipped in Solution 1 after it is dipped in Solution 2.
  • Solution 2 used in the above-described method may be a monomer solution not containing a dopant.
  • a solution containing an oxidizing agent may be allowed to be present together on use of the dopant.
  • Such an operation in the polymerization step is repeated once or more, preferably from 3 to 20 times, per the niobium sintered body having thereon a dielectric material, whereby a dense and stratified electrically conducting polymer layer can be easily formed.
  • any oxidizing agent may be used insofar as it does not adversely affect the capacitor performance and the reductant of the oxidizing agent can work out to a dopant and elevate the electrically conductivity of the electrically conducting polymer.
  • An industrially inexpensive compound facilitated in the handling at the production is preferred.
  • the oxidizing agent include Fe(III)-base compounds such as FeCl 3 , FeClO 4 and Fe (organic acid anion) salt; anhydrous aluminum chloride/cupurous chloride; alkali metal persulfates, ammonium persulfates; peroxides; manganeses such as potassium permanganate; quinones such as 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetrachloro-1,4-benzoquinone and tetracyano-1,4-benzoquinone; halogens such as iodine and bromine; peracid; sulfonic acid such as sulfuric acid, fuming sulfuric acid, sulfur trioxide, chlorosulfonic acid, fluorosulfonic acid and amidosulfuric acid; ozone, etc. and a mixture of a plurality of these oxidations.
  • Fe(III)-base compounds such as FeCl 3
  • Examples of the fundamental compound of the organic acid anion for forming the above-described Fe (organic acid anion) salt include organic sulfonic acid, organic carboxylic acid, organic phosphoric acid and organic boric acid, etc.
  • Specific examples of the organic sulfonic acid include benzenesulfonic acid, p-toluenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, ⁇ -sulfonaphthalene, ⁇ -sulfonaphthalene, naphthalenedisulfonic acid, alkylnaphthalenesulfonic acid (examples of the alkyl group include butyl, triisopropyl and di-tert-butyl), etc.
  • organic carboxylic acid examples include acetic acid, propionic acid, benzoic acid and oxalic acid.
  • polymer electrolyte anions such as polyacrylic acid, polymethacrylic acid, polystyrenesulfonic acid, polyvinylsulfonic acid, poly- ⁇ -methylsulfonic acid polyvinylsulfate, polyethylenesulfonic acid and polyphosphoric acid may also be used in the present invention.
  • organic sulfuric acids and organic carboxylic acids are mere examples and the present invention is not limited thereto.
  • Examples of the counter cation to the above-described anion include alkali metal ions such as H + , Na + and K + , and ammonium ions substituted by a hydrogen atom, a tetramethyl group, a tetraethyl group, a tetrabutyl group or a tetraphenyl group, however, the present invention is not limited thereto.
  • these oxidizing agents more preferred are trivalent Fe-base compounds and oxidizing agents comprising cuprous chloride, an alkali persulfate, an ammonium persulfate, an acid or a quinone.
  • an electrolyte anion having as a counter anion an oxidizing agent, anion (a reductant of oxidizing agent) produced from the above-described oxidizing agent, or other electrolyte anion may be used.
  • halide anion of Group 5B elements such as PF 6 - , SbF 6 - and AsF 6 -
  • halide anion of Group 3B elements such as BF 4 -
  • halogen anion such as I - (I 3 - ), Br - and Cl -
  • perhalogenate anion such as ClO 4 -
  • Lewis acid anion such as AlCl 4 - , FeCl 4 - and SnCl 5 -
  • inorganic acid anion such as NO 3 - and SO 4 2-
  • sulfonate anion such as p-toluenesulfonic acid, naphthalenesulfonic acid, and alkyl-substituted naphthalenesulfonic acid having from 1 to 5 carbon atoms (hereinafter simply referred to as "C1-5"); organic sulfonate anion such as CF 3 SO 3 - and CH 3
  • polymer electrolyte anions such as polyacrylic acid, polymethacrylic acid, polystyrenesulfonic acid, polyvinylsulfonic acid, polyvinylsulfonic acid, poly- ⁇ -methylsulfonic acid, polyethylenesulfonic acid and polyphosphoric acid may also be used, however, the present invention is not limited thereto.
  • the anion is preferably a polymer-type or oligomer-type organic sulfonic acid compound anion or a polyphosphoric acid compound anion.
  • an aromatic sulfonic acid compound e.g., podium dodecylbenzenesulfonate, sodium naphthalenesulfonate
  • the more effective dopant are a sulfoquinone compound having one or more sulfo-anion group (-SO 3 - ) within the molecule and a quinone structure, and an anthracene sulfonate anion.
  • Examples of the fundamental skeleton for the sulfoquinone anion of the above-described sulfoquinone compound include p-benzoquinone, o-benzoquinone, 1,2-naphthoquinone, 1,4-naphthoquinone, 2,6-naphthoquinone, 9,10-anthraquinone, 1,4-anthraquinone, 1,2-anthraquinone, 1,4-chrysenequinone, 5,6-chrysenequinone, 6,12-chrysenequinone, acenaphthoquinone, acenaphthenequinone, camphorquinone, 2,3-bornanedione, 9,10-phenanthrenequinone and 2,7-pyrenequinone.
  • an electrical conducting layer may be provided thereon so as to attain good electrical contact with an exterior leading line (for example, lead frame), if desired.
  • the electrical conducting layer can be formed, for example, by the solidification of an electrically conducting paste, plating, metallization or formation of a heat-resistant electrically conducting resin film.
  • Preferred examples of the electrically conducting paste include silver paste, copper paste, aluminum paste, carbon paste and nickel paste, and these may be used individually or in combination of two or more thereof. In the case of using two or more kinds of pastes, the pastes may be mixed or may be superposed one on another as separate layers.
  • the electrically conducting paste applied is then solidified by allowing it to stand in air or under heating.
  • the plating include nickel plating, copper plating, silver plating and aluminum plating.
  • Examples of the vapor-deposited metal include aluminum, nickel, copper and silver.
  • This capacitor may have a niobium or tantalum lead which is sintered and molded integrally with the lanthanum-containing niobium sintered body or welded afterward.
  • the thus-constructed capacitor of the present invention is jacketed using, for example, resin mold, resin case, metallic jacket case, dipping of resin or laminate film, and then used as a capacitor product for various uses.
  • the capacitor constructed by the above-described two electrodes and a dielectric material is housed, for example, in a can electrically connected to the another part electrode to form a capacitor.
  • the electrode side of the lanthanum-containing niobium sintered body is guided outside through a niobium or tantalum lead described above and at the same time, insulated from the can using an insulating rubber or the like.
  • the capacitor of the present invention has a large electrostatic capacitance for the volume as compared with conventional tantalum capacitors and more compact capacitor products can be obtained.
  • the capacitor having these properties of the present invention can be applied to uses as a bypass or coupling capacitor in an analog or digital circuit and as a large-capacitance smoothing capacitor used in the light source circuit and also to uses of conventional tantalum capacitor.
  • the capacitor of the present invention when used, a highly reliable electronic instrument more compact than conventional ones, such as computer, computer peripheral equipment such as PC card, mobile equipment such as portable telephone, home appliances, equipment mounted on a car, artificial satellite and communication equipment, can be obtained.
  • the capacitance and the leakage current value of the chip capacitor processed in the Examples were measured as follows.
  • tungsten-containing niobium ingot alloy containing 1 mol% of tungsten was prepared.
  • 50 g of the ingot was put into a reaction vessel made of stainless steel (SUS304), and hydrogen was continuously introduced into the vessel at 400°C for 10 hours.
  • the hydrogenated tungsten-containing niobium in the form of a cake was cooled and pulverized with balls made of stainless steel (SUS) for 10 hours in a pot made of stainless steel (SUS304).
  • the hydrogenated product prepared as a slurry in water in an amount of 20% by volume was placed in a wet pulverizer made of stainless steel (SUS304) (trademark "Atritor", made by Atlanta Corporation) together with zirconia balls and wet grinding was performed for 7 hours.
  • the slurry was subjected to centrifugal sedimentation, and the pulverized particles were obtained by decantation.
  • the pulverized particles were dried at 50°C under a vacuum of 133 Pa.
  • the hydrogenated tungsten-containing niobium powder was heated at 400°C for dehydrogenation under the application of a pressure of 1.33 x 10 -2 Pa for one hour.
  • the mean particle size of the obtained tungsten-containing niobium powder was 1.0 ⁇ m, and the content of tungsten was found to be 1 mol% when measured by atomic absorption analysis.
  • the tungsten-containing niobium powder thus obtained was granulated at 1150°C under a vacuum of 3.99 x 10 -3 Pa, and thereafter, subjected to disintegration. Thus, a granulated powder with a mean particle size of 150 ⁇ m was obtained.
  • the tungsten-containing niobium powder thus granulated was integrally molded with a niobium lead wire with a diameter of 0.3 mm, whereby a molded article with a size of around 0.3 cm x 0.18 cm x 0.45cm, weighing about 0.1 g, was produced.
  • the molded article was allowed to stand at 1200°C under a vacuum of 3.99 x 10 -3 Pa for 30 minutes, thereby obtaining a sintered body.
  • the obtained sintered body was subjected to forming in a 0.1-% aqueous solution of phosphoric acid at 80°C under the application of a voltage of 20 V for 200 minutes, so that a dielectric layer was deposited on the surface of the sintered body.
  • the capacitance of the sintered body in 30% sulfuric acid, and the leakage current of the sintered body (hereinafter referred to as "LC") in a 20% aqueous solution of phosphoric acid were separately measured. The results are shown in TABLE 5.
  • a niobium sintered body containing at least one of the above-mentioned transition elements of group 6 in the periodic table that is, at least one element selected from the group consisting of chromium, molybdenum, and tungsten
  • the transition element(s) of group 6 of the periodic table in the form of a powder and a niobium ingot were mixed in an arbitrary ratio.
  • a niobium ingot containing the transition element of the group 6 of the periodic table was prepared by arc fusion.
  • the niobium ingot, which weighed 50 g, was pulverized using the same apparatus as employed in Example 2 with the pulverizing time being changed.
  • a sintered body was produced.
  • the capacitance and the LC of the sintered body were separately measured. TABLE 5 shows the results.
  • a niobium powder containing no transition element of group 6 of the periodic table was prepared in the same manner as in Example 1 in order to compare the results of Examples 1 to 9.
  • a sintered body was produced by following the same procedures as in Example 1, and the capacitance and the LC of the sintered body were measured.
  • TABLE 5 shows the results.
  • niobium and tungsten were varied before arc fusion in order to change the content of tungsten in the obtained tungsten-containing niobium.
  • a niobium ingot containing tungsten in an amount of 0.01 to 10 mol% was prepared.
  • a sintered body was prepared from 50 g of the tungsten-containing niobium ingot having each concentration of tungsten in the same manner as in Example 1. The capacitance and the LC were separately measured. TABLE 8 shows the results.
  • a niobium ingot containing 0 mol% of tungsten, and a niobium ingot containing 15.5 mol% of tungsten were prepared to compare the results of Examples 10 to 15.
  • a sintered body was prepared from 50 g of the tungsten-containing niobium ingot having each concentration of tungsten in the same manner as in Example 1. The capacitance and the LC were separately measured. TABLE 6 shows the results.
  • a niobium ingot 100 g was put into a reaction vessel made of stainless steel (SUS304), and hydrogen was continuously introduced into the vessel at 400°C for 10 hours.
  • the hydrogenated niobium in the form of a cake was cooled and pulverized with balls made of stainless steel (SUS) for 10 hours in a pot made of stainless steel (SUS304).
  • the hydrogenated product was prepared as a slurry in water in an amount of 20% by volume and placed in a wet pulverizer made of stainless steel (SUS304) (trademark "Atritor") together with zirconia balls, and wet grinding was performed for 7 hours.
  • the slurry was subjected to centrifugal sedimentation, and the pulverized particles were obtained by decantation.
  • the pulverized particles were dried at 50°C under a vacuum of 133 Pa. Subsequently, the hydrogenated niobium powder was heated at 400°C for dehydrogenation under the application of a pressure of 1.33 x 10 -2 Pa for one hour. The mean particle size of the obtained niobium powder was 1.3 ⁇ m.
  • the tungsten-containing niobium powder thus obtained was granulated at 1150°C under a vacuum of 3.99 x 10 -3 Pa, and thereafter, subjected to disintegration. Thus, a granulated powder with a mean particle size of 190 ⁇ m was obtained.
  • the tungsten-containing niobium granulated powder was integrally molded with a niobium lead wire with a diameter of 0.3 mm, whereby a molded article with a size of around 0.3 cm x 0.18 cm x 0.45 cm, weighing about 0.1 g, was produced.
  • the molded article was allowed to stand at 1230°C under a vacuum of 3.99 x 10 -3 Pa for 30 minutes, thereby obtaining a sintered body.
  • the obtained sintered body was subjected to forming in a 0.1% aqueous solution of phosphoric acid at 80°C under the application of a voltage of 20 V for 200 minutes, so that a dielectric layer was deposited on the surface of the sintered body.
  • the capacitance of the sintered body in 30% sulfuric acid, and the LC of the sintered body in a 20% aqueous solution of phosphoric acid were separately measured. The results are shown in TABLE 7.
  • tungsten-containing niobium nitride 10 g of the tungsten-containing niobium powder with a mean particle size of 0.9 ⁇ m, containing tungsten in an amount of 1.2 mol%, prepared by the same method as in Example 15, was put into a reaction vessel made of stainless steel (SUS304) With nitrogen introduced into the vessel at 300°C for 0.5 to 20 hours, a tungsten-containing niobium nitride was obtained.
  • the amount of nitrogen in the niobium nitride was determined using an apparatus made by LECO Corporation for determining nitrogen content based on thermal conductivity.
  • the ratio of the amount of nitrogen to the mass of the powder separately measured was defined as the nitride content.
  • the nitride content was 0.02 to 0.89% by mass.
  • the tungsten-containing niobium nitride thus obtained was subjected to the same steps of granulation, molding, and sintering as in Example 1, so that a sintered body was prepared.
  • the obtained sintered body was subjected to forming in a 0.1% aqueous solution of phosphoric acid at 80°C under the application of a voltage of 20 V for 200 minutes, so that a dielectric layer was deposited on the surface of the sintered body.
  • the capacitance of the sintered body in 30% sulfuric acid, and the LC of the sintered body in a 20% aqueous solution of phosphoric acid were separately measured. The results are shown in TABLE 8.
  • a tungsten-containing niobium powder with a mean particle size of 1.0 ⁇ m containing tungsten in an amount of 10 mol% was prepared by the same method as in Example 1. Apart from this, sodium was added to 20 g of potassium fluoroniobate fully dried at 80°Cyunder vacuum in a nickel crucible so that the amount of sodium was 10 times the molar amount of potassium fluoroniobate. Then, reduction was carried out at 1000°C in an atmosphere of argon for 20 hours. After completion of the reduction reaction, the reduced product was cooled, and successively washed with water, 95% sulfuric acid, and water, and thereafter dried under vacuum.
  • the resulting product was pulverized for 40 hours using a ball mill, that is, an alumina pot provided with silica-alumina balls. Then, the pulverized product was immersed in a liquid mixture of 50% nitric acid and a 10% aqueous solution of hydrogen peroxide in a ratio by mass of 3:2, with stirring. The pulverized product was thoroughly washed with water to remove impurities until the pH of the product reached 7, and dried under vacuum. The mean particle size of the obtained niobium powder was 1.2 ⁇ m.
  • the tungsten-containing niobium powder and the niobium powder separately prepared by the above-mentioned methods were sufficiently mixed in an arbitrary ratio, and the mixture was subjected to the same steps of granulation, molding, and sintering as in Example 15, thereby obtaining a sintered body.
  • the capacitance and the LC of the sintered body were separately measured. TABLE 9 shows the results.
  • a tungsten-containing niobium powder with a mean particle size of 1.0 ⁇ m containing tungsten in an amount of 10 mol% was prepared by the same method as in Example 15. Apart from this, 50 g of a niobium ingot was put into a reaction vessel made of stainless steel (SUS304), and hydrogen was continuously introduced into the vessel at 400°C for 12 hours. The hydrogenated niobium in the form of a cake was cooled and pulverized with iron balls for 10 hours in a pot made of stainless steel (SUS304).
  • the pulverized product was put into the same reaction vessel made of stainless steel (SUS304) as mentioned above, and again hydrogenated under the same conditions as mentioned above.
  • the hydrogenated product was prepared as a slurry in water in an amount of 20% by volume and placed in a wet pulverizer made of stainless steel (SUS304) (trademark "Atritor”) together with zirconia balls and wet grinding was performed for 6 hours.
  • the slurry was subjected to centrifugal sedimentation, and the pulverized particles were obtained by decantation.
  • the pulverized particles were dried at 50°C under a vacuum of 133 Pa.
  • the hydrogenated niobium powder was heated at 400°C for dehydrogenation under a pressure of 1.33 x 10 -2 Pa for one hour.
  • the mean particle size of the obtained niobium powder was 1.3 ⁇ m.
  • the tungsten-containing niobium powder and niobium powder thus obtained were sufficiently mixed in an arbitrary ratio, and a nitride was obtained in the same manner as in Example 25.
  • the tungsten-containing niobium nitride was subjected to the steps of granulation, molding, and sintering, so that a sintered body was prepared. Then, the capacitance and the LC of the sintered body were separately measured. The results are shown in TABLE 9.
  • Example 34 and Example 35 50 units of sintered bodies were prepared in the same manner as in Example 1 and Example 11 respectively.
  • a voltage of 20 V was applied to each sintered body for 200 minutes in a 0.1% aqueous solution of phosphoric acid, whereby a dielectric oxide film was deposited on the surface of the sintered body by electrolytic forming.
  • the steps of immersing the dielectric-film-bearing sintered body in a 60% aqueous solution of manganese nitrate and heating at 220°C for 30 minutes were repeated, so that a manganese dioxide layer serving as the counter electrode layer was formed on the dielectric oxide film.
  • a carbon layer and a silver paste layer were successively overlaid on the counter electrode layer.
  • the LC value was a value obtained at room temperature under a voltage of 6.3 V for one minute.
  • Example 36 and Example 37 50 units of sintered bodies were prepared in the same manner as in Example 8 and Example 15 respectively. A voltage of 20 V was applied to each sintered body for 200 minutes in a 0.1% aqueous solution of phosphoric acid, whereby a dielectric oxide film' was deposited on the surface of the sintered body by electrolytic forming.
  • the LC value was a value obtained at room temperature under a voltage of 6.3 V for one minute.
  • Example 38 Example 39, and Example 40, 50 units of sintered bodies were prepared in the same manner as in Example 7, Example 12, and Example 25, respectively.
  • a voltage of 20 V was applied to each sintered body for 200 minutes in a 0.1% aqueous solution of phosphoric acid, whereby a dielectric oxide film was deposited on the surface of the sintered body by electrolytic forming.
  • the steps of bringing the dielectric-film-bearing sintered body into contact with a liquid mixture of a 10% aqueous solution of ammonium persulfate and a 0.5% aqueous solution of anthraquinonesulfonic acid in a mixing ratio by volume of 1:1 and exposing the dielectric oxide film to a pyrrole gas were repeated at least 5 times, so that the other electrode (counter electrode) of polypyrrole was formed on the dielectric oxide film.
  • the pulverized product was immersed in a liquid mixture of 50% nitric acid and a 10% aqueous solution of hydrogen peroxide in a ratio by mass of 3:2, with stirring.
  • the pulverized product was thoroughly washed with water to remove impurities until the pH of the product reached 7, and dried under vacuum.
  • the mean particle size of the obtained niobium powder was 1.3 ⁇ m.
  • 30 g of the niobium powder thus prepared was put into a reaction vessel made of stainless steel (SUS304), with nitrogen introduced therein at 300°C for 0.5 to 4 hours. Thus, a niobium nitride was obtained.
  • the amount of nitrogen in the niobium nitride was determined using an apparatus made by LECO Corporation for determining nitrogen content based on thermal conductivity.
  • the ratio of the amount of nitrogen to the mass of the powder separately measured was defined as the nitride content.
  • the nitride content was 0.02 to 0.30% by mass.
  • the niobium nitride thus obtained was subjected to the same steps of granulation, molding, and sintering as in Example 1, so that a sintered body was prepared.
  • a voltage of 20 V was applied to each sintered body for 200 minutes in a 0.1% aqueous solution of phosphoric acid, whereby a dielectric oxide film was deposited on the surface of the sintered body by electrolytic forming. Then, the steps of immersing the dielectric-film-bearing sintered body in a 60% aqueous solution of manganese nitrate and heating the sintered body at 220°C for 30 minutes were repeated, so that a manganese dioxide layer serving as the counter electrode layer was formed on the dielectric oxide film. Subsequently, a carbon layer and a silver paste layer were successively overlaid on the counter electrode.
  • the LC value was a value obtained at room temperature under a voltage of 6.3 V for one minute.
  • niobium ingot 50 g was put into a reaction vessel made of stainless steel (SUS304), and hydrogen was continuously introduced into the vessel at 400°C for 12 hours.
  • the hydrogenated niobium in the form of a cake was cooled and pulverized with iron balls for 10 hours in a pot made of stainless steel (SUS304).
  • the pulverized product was put into the same reaction vessel made of stainless steel (SUS304) as mentioned above, and again hydrogenated under the same conditions as mentioned above.
  • the hydrogenated product was prepared as a slurry in water in an amount of 20% by volume and placed in a wet pulverizer made of stainless steel (SUS304) (trademark "Atritor”) together with, zirconia balls and wet grinding was performed for 6 hours.
  • the slurry was subjected to centrifugal sedimentation, and the pulverized particles were obtained by decantation.
  • the pulverized particles were dried at 50°C under a vacuum of 133 Pa.
  • the hydrogenated niobium powder was heated at 400°C for dehydrogenation under a pressure 1.33 x 10 -2 Pa for one hour.
  • the mean particle size of the obtained niobium powder was 1.0 ⁇ m.
  • 30 g of the niobium powder was put into a reaction vessel made of stainless steel (SUS304), with nitrogen being introduced therein at 300°C for 0.5 to 3 hours, thereby obtaining a niobium nitride.
  • the amount of nitrogen in the niobium nitride was determined using an apparatus made by LECO Corporation for determining nitrogen content based on thermal conductivity. The ratio of the amount of nitrogen to the mass of the powder separately measured was defined as the nitride content.
  • the nitride content was 0.03 to 0.28% by mass.
  • the niobium nitride thus obtained was subjected to the same steps of granulation, molding, and sintering as in Example 1, so that a sintered body was prepared. With respect to 50 units of sintered bodies, a voltage of 20 V was applied to each sintered body for 200 minutes in a 0.1% aqueous solution of phosphoric acid, whereby a dielectric oxide film was deposited on the surface of the sintered body by electrolytic forming.
  • the steps of bringing the dielectric-film-bearing sintered body into contact with a liquid mixture of a 10% aqueous solution of ammonium persulfate and a 0.5% aqueous solution of anthraquinonesulfonic acid in a mixing ratio by volume of 1:1 and exposing the dielectric oxide film to a pyrrole gas were repeated at least 5 times, so that the counter electrode of polypyrrole was formed on the dielectric oxide film. Subsequently, a carbon layer and a silver paste layer were successively overlaid on the counter electrode.
  • the LC value was a value obtained at room temperature under a voltage of 6.3 V for one minute.
  • Example 41 50 units of sintered bodies were prepared in the same manner as in Example 25. A voltage of 20 V was applied to each sintered body for 200 minutes in a 0.1% aqueous solution of phosphoric acid, whereby a dielectric oxide film was deposited on the surface of the sintered body by electrolytic forming. Then, the niobium sintered body was immersed in an aqueous solution containing ammonium persulfate in an amount of 25% by mass (solution 1A) removed from the solution 1A, and dried at 80°C for 30 minutes, thereby forming a dielectric.
  • solution 1A aqueous solution containing ammonium persulfate in an amount of 25% by mass
  • the dielectric-deposited sintered body was immersed in an isopropanol solution containing 3, 4-ethylenedioxythiophene in an amount of 18% by mass (solution 2), removed from the solution 2, and allowed to stand at 60°C for 10 minutes, thereby carrying out oxidative polymerization.
  • the resultant product was immersed in the solution 1A again, and underwent the same steps as mentioned above. After the procedure from immersion in the solution 1A to oxidative polymerization was repeated 8 times, the resultant product was washed with hot water of 50°C for 10 minutes, and then dried at 100°C for 30 minutes, thereby forming the other electrode (counter electrode) comprising electroconducting poly (3, 4-ethylenedioxythiophene).
  • Example 12 50 units of sintered bodies were prepared in the same manner as in Example 12. A voltage of 20 V was applied to each sintered body for 200 minutes in a 0.1% aqueous solution of phosphoric acid, whereby a dielectric oxide film was deposited on the surface of the sintered body by electrolytic forming. Then, the niobium sintered body was immersed in an aqueous solution containing ammonium persulfate in an amount of 25% by mass and sodium anthraquinone-2-sulfonate in an amount of 3% by mass (solution 1B), removed from the solution 1B, and dried at 80°C for 30 minutes, thereby forming a dielectric.
  • solution 1B aqueous solution containing ammonium persulfate in an amount of 25% by mass and sodium anthraquinone-2-sulfonate in an amount of 3% by mass
  • the dielectric-deposited sintered body was immersed in an isopropanol solution containing 3,4-ethylenedioxythiophene in an amount of 18% by mass (solution 2), removed from the solution 2, and allowed to stand at 60°C for 10 minutes, thereby carrying out oxidative polymerization.
  • the resultant product was immersed in the solution 1B again, and underwent the same steps as mentioned above. After the procedure from immersion in the solution 1B to oxidative ' polymerization was repeated 8 times; the resultant product was washed with hot water of 50°C for 10 minutes, and then dried at 100°C for 30 minutes, thereby forming the other electrode (counter electrode) comprising electroconducting poly(3,4-ethylenedioxythiophene): ..
  • a boron-containing niobium ingot (alloy) having a boron content of 2 mol% was produced by arc melting.
  • an SUS 304-made reactor 50 g of the obtained ingot was placed and hydrogen was continuously introduced thereinto at 400°C for 10 hours. After cooling, the hydrogenated boron-containing niobium cake placed in an SUS 304-made pot containing SUS-made balls and pulverized for 10 hours.
  • this hydride was formed into a 20 vol% slurry with water, charged together with zirconia balls into an SUS 304-made spike mill, and wet-pulverized at 10°C or less for 7 hours.
  • the resulting slurry was subjected to centrifugal sedimentation and decanted to obtain a pulverized product.
  • the pulverized product was dried in a vacuum under the conditions of 1.33 ⁇ 10 2 Pa and 50°C.
  • the hydrogenated boron-containing niobium powder was dehydrogenated under heating at 1.33 ⁇ 10 -2 Pa and 400°C for 1 hour.
  • the produced boron-containing niobium powder had a mean particle size of 1.0 ⁇ m and the boron content thereof was measured by the atomic absorption analysis and found to be 2 mol%.
  • the thus-obtained boron-containing niobium powder was granulated in a vacuum of 3.99 ⁇ 10 -3 Pa at 1,000°C. Thereafter, the granulated cake was pulverized to obtain a granulated powder having a mean particle size of 100 ⁇ m.
  • the thus-obtained boron-containing niobium granulated powder was molded together with a 0.3-mm ⁇ niobium lead wire to manufacture a molded article having a size of approximately 0.3 ⁇ 0.18 ⁇ 0.45 cm (weighing about 0.1 g).
  • This molded article was allowed to stand in a vacuum of 3.99 ⁇ 10 -3 Pa at 1,200°C for 30 minutes and thereby, a sintered body was obtained.
  • the sintered body obtained was electrochemically formed in an aqueous 0.1% phosphoric acid solution at a temperature of 80°C for 200 minutes by applying a voltage of 20 V to form a dielectric layer on the surface. Thereafter, the capacitance in 30% sulfuric acid and the leakage current (LC) in an aqueous 20% phosphoric acid solution were measured. The results obtained are shown in Table 11.
  • the hydrogenated niobium powder was dehydrogenated under heating at 1.33 ⁇ 10 -2 Pa and 400°C for 1 hour.
  • the manufactured niobium powder had a mean particle size of 1.1 ⁇ m.
  • any one of niobium diboronate, boron oxide and boron metal each having a mean particle size of about 1 ⁇ m was mixed at an arbitrary ratio.
  • the obtained boron-containing niobium powder was granulated in a vacuum of 3.99 ⁇ 10 -3 Pa at 1,050°C. Thereafter, the granulated cake was pulverized to obtain a granulated powder having a mean particle size of 90 ⁇ m.
  • the thus-obtained boron-containing niobium granulated powder was molded together with a 0.3-mm ⁇ niobium lead wire to manufacture a molded article having a size of approximately 0.3 ⁇ 0.18 ⁇ 0.45 cm (weighing about 0.1 g). Subsequently, these molded articles were allowed to stand in a vacuum of 3.99 ⁇ 10 -3 Pa at 1,200°C for 30 minutes to obtain sintered bodies.
  • the resulting sintered bodies each was electrochemically formed in an aqueous 0.1% phosphoric acid solution at a temperature of 80°C for 200 minutes by applying a voltage of 20 V to form a dielectric layer on the surface.
  • boron-containing niobium powder containing 6. 9 mol% of boron and having a mean particle size of 1.0 ⁇ m was obtained in the same manner as in Example 43.
  • 50 g of a niobium ingot was placed in an SUS 304-made reactor and hydrogen was continuously introduced thereinto at 400°C for 12 hours. After cooling, the hydrogenated niobium cake was placed in an SUS 304-made pot containing iron-made balls and pulverized for 10 hours.
  • This pulverized product was charged into the same SUS 304-made reactor as above and again hydrogenated under the above-described conditions. Thereafter, this hydride was formed into a 20 vol% slurry with water, charged together with zirconia balls into an SUS 304-made spike mill, and wet-pulverized for 6 hours.
  • the resulting slurry was centrifuged and decanted to obtain a pulverized product.
  • the pulverized product was dried in a vacuum under the conditions of 1.33 ⁇ 10 2 Pa and 50°C.
  • the hydrogenated niobium powder was dehydrogenated under heating in a vacuum of 1.33x10 -2 Pa at 400°C for 1 hour.
  • the manufactured niobium powder had a mean particle size of 1.1 ⁇ m.
  • Example 81 and Example 82 50 Units of sintered bodies were prepared in each of Example 81 and Example 82 in same manner as in Example 43 and Example 44, respectively. These sintered bodies each was electrochemically formed using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 200 minutes to form an oxide dielectric film on the surface. Subsequently, an operation of dipping each sintered body in an aqueous 60% manganese nitrate solution and then heating it at 220°C for 30 minutes was repeated to form a manganese dioxide layer as the other electrode (counter electrode) layer on the oxide dielectric film. On this counter electrode layer, a carbon layer and a silver paste layer were stacked in this order.
  • the device as a whole was molded with an epoxy resin to manufacture a chip-type capacitor.
  • the LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.
  • the LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.
  • Example 89 Units of sintered bodies were prepared in each of Example 89, Example 90, Example 91, Example 92 and Example 93 in same manner as in Example 59, Example 50, Example 65, Example 72 and Example 76, respectively.
  • These sintered bodies each was electrochemically formed using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 200 minutes to form an oxide dielectric film on the surface.
  • the niobium sintered body was dipped into an aqueous solution containing 25% by mass of ammonium persulfate (Solution 1), then pulled up and dried at 80°C for 30 minutes.
  • Solution 1 ammonium persulfate
  • the sintered body having formed thereon a dielectric material was dipped in an isopropanol solution containing 18% by mass of 3,4-ethylenedioxythiophene (Solution 2), then pulled up and left standing in an atmosphere of 60°C for 10 minutes to allow the oxidation-polymerization to proceed.
  • the resulting sintered body was again dipped in Solution 1 and then treated in the same manner as above. The operation from the dipping in Solution 1 until the oxidation polymerization was repeated 8 times.
  • the sintered body was washed with hot water at 50°C for 10 minutes and dried at 100°C for 30 minutes, whereby the other electrode (counter electrode) comprising electrically conducting poly(3,4-ethylenedioxythiophene) was formed.
  • the LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.
  • the manufactured niobium powder had a mean particle size of 1.3 ⁇ m.
  • 30 g of the thus-obtained niobium powder was charged and thereinto, nitrogen was continuously introduced at 300°C for 0.5 to 4 hours to obtain niobium nitrides.
  • the nitrogen amount of each nitride was determined using the nitrogen amount measuring apparatus manufactured by LECO which determines the nitrogen amount from the thermal conductivity.
  • the ratio of the measured value to the separately measured mass of powder was designated as the nitrided amount, as a result, the nitrided amount here was from 0.02 to 0.30% by mass.
  • Each niobium nitride was granulated, molded and sintered in the same manner as in Example 43 to obtain a sintered body.
  • the thus-obtained 50 units of sintered bodies each was electrochemically formed using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 200 minutes to form an oxide dielectric film on the surface.
  • the resulting slurry was subjected to centrifugal sedimentation decanted to obtain a pulverized product.
  • the pulverized product was vacuum-dried in a vacuum of 1.33 ⁇ 10 2 Pa at 50°C.
  • the hydrogenated niobium powder was dehydrogenated under heating in a vacuum of 1.33 ⁇ 10 -2 Pa at 400°C for 1 hour.
  • the manufactured niobium powder had a mean particle size of 1.0 ⁇ m.
  • 30 g of the obtained niobium powder was charged and thereinto, nitrogen was continuously introduced at 300°C for 0.5 to 3 hours to obtain niobium nitrides.
  • the nitrogen amount of each nitride was determined using a nitrogen amount measuring apparatus manufactured by LECO which determines the nitrogen amount from the thermal conductivity.
  • the ratio of the measured value to the separately measured mass of powder was designated as the nitrided amount, as a result, the nitrided amount here was from 0.03 to 0.28% by mass.
  • Each niobium nitride was granulated, molded and sintered in the same manner as in Example 43 to obtain a sintered body.
  • the thus-obtained 50 units of sintered bodies each was electrochemically formed using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 200 minutes to form an oxide dielectric film on the surface.
  • the LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.
  • TABLE 16 Nitrogen Content (mass %) Capacitance ( ⁇ F)
  • LC ( ⁇ A) Number of Units Having LC Exceeding 100 ⁇ A
  • a rhenium-containing niobium ingot (alloy) having a rhenium content of 1 mol% was produced by arc melting.
  • an SUS 304-made reactor 50 g of the obtained ingot was placed and hydrogen was continuously introduced thereinto at 400°C for 10 hours. After cooling, the hydrogenated rhenium-containing niobium cake was placed in an SUS 304-made pot containing SUS-made balls and pulverized for 10 hours.
  • this hydride was formed into a 20 vol% slurry with water, charged together with zirconia balls into an SUS 304-made spike mill, and wet-pulverized at 10°C or less for 7 hours.
  • the resulting slurry was subjected to centrifugal sedimentation and decanted to obtain a pulverized product.
  • the pulverized product was dried in a vacuum under the conditions of 1.33 ⁇ 10 2 Pa and 50°C.
  • the hydrogenated rhenium-containing niobium powder was dehydrogenated under heating at 1.33 ⁇ 10 -2 Pa and 400°C for 1 hour.
  • the produced rhenium-containing niobium powder had a mean particle size of 1 ⁇ m and the rhenium content thereof was measured by the atomic absorption analysis and found to be 1 mol%.
  • the thus-obtained rhenium-containing niobium powder was granulated in a vacuum of 4 ⁇ 10 -3 Pa at 1,000°C. Thereafter, the granulated cake was pulverized to obtain a granulated powder having a mean particle size of 100 ⁇ m.
  • the thus-obtained rhenium-containing niobium granulated powder was molded together with a 0.3-mm ⁇ niobium lead wire to manufacture a molded article having a size of approximately 0.3 ⁇ 0.18 ⁇ 0.45 cm (weighing about 0.1 g).
  • This molded article was allowed to stand in a vacuum of 4 ⁇ 10 -3 Pa at 1,200°C for 30 minutes and thereby, a sintered body was obtained.
  • the sintered body obtained was electrochemically formed in an aqueous 0.1% phosphoric acid solution at a temperature of 80°C for 200 minutes by applying a voltage of 20 V to form a dielectric layer on the surface. Thereafter, the capacitance in 30% sulfuric acid and the leakage current (hereinafter simply referred to as "LC") in an aqueous 20% phosphoric acid solution were measured. The results obtained are shown in Table 17.
  • a niobium sintered body comprising at least one element of cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic and bismuth
  • a powder of cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic or bismuth and a niobium ingot were used at an arbitrary ratio and niobium ingots containing at least one element of cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic and bismuth were produced by arc melting.
  • Example 2 Thereafter, 50 g of each ingot was pulverized using the same apparatus as in Example 1 by changing the pulverization time. Using the thus-obtained niobium powder containing cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic or bismuth, sintered bodies were manufactured and each was measured on the capacitance and LC. The results obtained are shown in Table 17.
  • Rhenium has an effect of giving a lowest leakage current value and zinc, arsenic, phosphorus, germanium and tin follow in this order.
  • the leakage current value is almost the same among cerium, neodymium, titanium, ruthenium, rhodium, palladium, silver, silicon and bismuth, and follows that of tin.
  • the niobium powder most preferably contains rhenium and next preferably zinc.
  • niobium powder not containing any of cerium, neodymium, titanium, rhenium, ruthenium, rhodium, palladium, silver, zinc, silicon, germanium, tin, phosphorus, arsenic and bismuth and having a different mean particle size were produced in the same manner as in Example 94.
  • sintered bodies were manufactured and measured on the capacitance and LC. The results obtained are shown in Table 17. TABLE 17 Composition(Molar ratio) Mean Parti cle Size ( ⁇ m) Capacitance ( ⁇ F• V/g) LC ( ⁇ A/g) Ex.
  • rhenium-containing niobium ingots having a rhenium content of 0.01 to 7 mol% were produced while varying the amounts of niobium and rhenium processed by the arc melting. Thereafter, using 50 g of each of the rhenium-containing niobium ingots having respective rhenium concentrations, sintered bodies were manufactured by the same operation as in Example 94 and each was measured on the capacitance and LC. The results obtained are shown in Table 18.
  • Example 94 For the purpose of comparison with Example 94 and Examples 118 to 122, rhenium-containing niobium ingots containing 0 mol%, 11 mol% or 18 mol% of rhenium were produced. Thereafter, using 50 g of each of the rhenium-containing niobium ingots having respective rhenium concentrations, sintered bodies were manufactured by the same operation as in Example 94 and each was measured on the capacitance and LC. The results obtained are shown in Table 18.
  • any one of rhenium oxide, rhenium sulfide and rhenium metal each having a mean particle size of about 1 ⁇ m was mixed at an arbitrary ratio.
  • the obtained rhenium-containing niobium powder was granulated in a vacuum of 4 ⁇ 10 -3 Pa at 1,050°C. Thereafter, the granulated cake was cracked to obtain a granulated powder having a mean particle size of 90 ⁇ m.
  • the thus-obtained rhenium-containing niobium granulated powder wasmolded together with a 0.3-mm ⁇ niobium lead wire to manufacture a molded article having a size of approximately 0.3x0.18x0.45 cm 3 (weighing about 0.1 g). Subsequently, these molded articles were allowed to stand in a vacuum of 4 ⁇ 10 -3 Pa at 1,200°C for 30 minutes to obtain sintered bodies.
  • the resulting sintered bodies each was electrochemically formed in an aqueous 0.1% phosphoric acid solution at a temperature of 80°C for 200 minutes by applying a voltage of 20 V to form a dielectric layer on the surface.
  • rhenium-containing niobium nitride 10 g of rhenium-containing niobium powder containing 0.9 mol% of rhenium and having a mean particle size of 0.9 ⁇ m was manufactured in the same manner as in Example 94 and charged into an SUS 304-made reactor and thereinto, nitrogen was continuously introduced at 300°C for 0.5 to 20 hours to obtain rhenium-containing niobium nitrides.
  • the nitrogen amount of each nitride was determined using a nitrogen amount measuring apparatus manufactured by LECO, which determines the nitrogen amount from the thermal conductivity.
  • the ratio of the measured value to the separately measured mass of powder was designated as the nitrided amount.
  • the nitrided amount here was from 0.02 to 0.79% by mass.
  • each sintered body obtained was electrochemically formed in an aqueous 0.1% phosphoric acid solution at a temperature of 80°C for 200 minutes by applying a voltage of 20 V to form a dielectric layer on the surface. Thereafter, the capacitance in 30% sulfuric acid and the LC value in an aqueous 20% phosphoric acid solution were measured. The results obtained are shown in Table 20.
  • a rhenium-containing niobium powder containing 10 mol% of rhenium and having a mean particle size of 1. 0 ⁇ m was obtained in the same manner as in Example 94.
  • the pulverized product was dipped and stirred in a 3:2 (by mass) mixed solution of 50% nitric acid and 10% aqueous hydrogen peroxide. Thereafter, the pulverized product was thoroughly washed with water until the pH reached 7 to remove impurities, and dried in a vacuum.
  • the produced niobium powder had a mean particle size of 1.2 ⁇ m.
  • rhenium-containing niobium powder containing 10 mol% of rhenium and having a mean particle size of 1.0 ⁇ m was obtained in the same manner as in Example 94.
  • 50 g of a niobium ingot was placed in an SUS 304-made reactor and hydrogen was continuously introduced thereinto at 400°C for 12 hours. After cooling, the hydrogenated niobium cake was placed in an SUS 304-made pot containing iron-made balls and pulverized for 10 hours.
  • This pulverized product was charged into the same SUS 304-made reactor as above and again hydrogenated under the above-described conditions. Thereafter, this hydride was formed into a 20 vol% slurry with water, charged together with zirconia balls into an SUS 304-made spike mill, and wet-pulverized for 6 hours.
  • the resulting slurry was subjected to centrifugal sedimentation and decanted to obtain a pulverized product.
  • the pulverized product was dried in a vacuum under the conditions of 1.33x10 2 Pa and 50°C.
  • the hydrogenated niobium powder was dehydrogenated under heating in a vacuum of 133 ⁇ 10 -2 Pa at 400°C for 1 hour.
  • the manufactured niobium powder had a mean particle size of 1.1 ⁇ m.
  • the thus-obtained rhenium-containing niobium powder was thoroughly mixed with niobium powder at an arbitrary ratio and after obtaining nitrides in the same manner as in Example 131, the nitrides each was granulated, molded and sintered to obtain sintered bodies. The capacitance and the LC value of each sintered body were measured and the results obtained are shown in Table 21.
  • Example 140 and Example 141 50 Units of sintered bodies were prepared in each of Example 140 and Example 141 in the same manner as in Example 94 and Example 116, respectively. These sintered bodies each was electrochemically formed using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 200 minutes to form an oxide dielectric film on the surface. Subsequently, an operation of dipping each sintered body in an aqueous 60% manganese nitrate solution and then heating it at 220°C for 30 minutes was repeated to form a manganese dioxide layer as the other electrode (counter electrode) layer on the oxide dielectric film. On this counter electrode layer, a carbon layer and a silver paste layer were stacked in this order.
  • the device as a whole was molded with an epoxy resin to manufacture a chip-type capacitor.
  • the LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.
  • Example 144 50 Units of sintered bodies were prepared in each of Example 144, Example 145, Example 146 and Example 147 in the same manner as in Example 96, Example 115, Example 132 and Example 97, respectively.
  • These sintered bodies each was electrochemically formed using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 200 minutes to form an oxide dielectric film on the surface.
  • an operation of contacting the oxide dielectric film with an equivalent-mass mixed solution of an aqueous 10% ammonium persulfate solution and an aqueous 0.5% anthraquinonesulfonic acid solution and then with a pyrrole vapor was repeated at least 5 times, whereby the other electrode (counter electrode) comprising polypyrrole was formed on the oxide dielectric film.
  • the LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.
  • Example 148 50 Units of sintered bodies were prepared in each of Example 148, Example 149, Example 150, Example 151, Example 152 and Example 153 in the same manner as in Example 114, Example 122, Example 123, Example 124, Example 131 and Example 136, respectively.
  • These sintered bodies each was electrochemically formed using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 200 minutes to form an oxide dielectric film on the surface. Subsequently, the niobium sintered body was dipped into an aqueous solution containing 25% by mass of ammonium persulfate (Solution 1), then pulled up and dried at 80°C for 30 minutes.
  • Solution 1 ammonium persulfate
  • the sintered body having formed thereon a dielectric material was dipped, in an isopropanol solution containing 18% by mass of 3,4-ethylenedioxythiophene (Solution 2), then pulled up and left standing in an atmosphere of 60°C for 10 minutes to allow the oxidation-polymerization to proceed.
  • the resulting sintered body was again dipped in Solution 1 and then treated in the same manner as above. The operation from the dipping in Solution 1 until the oxidation polymerization was repeated 8 times.
  • the sintered body was washed with hot water at 50°C for 10 minutes and dried at 100°C for 30 minutes, whereby the other electrode (counter electrode) comprising electrically conducting poly(3,4-ethylenedioxythiophene) was formed.
  • the LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.
  • the manufactured niobium powder had a mean particle size of 1.3 ⁇ m
  • 30 g of the thus-obtained niobium powder was charged and thereinto, nitrogen was continuously introduced at 300°C for 0.5 to 4 hours to obtain niobium nitrides.
  • the nitrogen amount of each nitride was determined using the nitrogen amount measuring apparatus manufactured by LECO which determines the nitrogen amount from the thermal conductivity.
  • the ratio of the measured value to the separately measured mass of powder was designated as the nitrided amount, as a result, the nitrided amount here was from 0.02 to 0.30% by mass.
  • Each niobium nitride was granulated, molded and sintered in the same manner as in Example 1 to obtain a sintered body.
  • the resulting slurry was subjected to centrifugal sedimentation and decanted to obtain a pulverized product.
  • the pulverized product was dried in a vacuum of 1.33x10 2 Pa at 50°C.
  • the hydrogenated niobium powder was dehydrogenated under heating in a vacuum of 1.33x10 -2 Pa at 400°C for 1 hour
  • the manufactured niobium powder had a mean particle size of 1.0 ⁇ m.
  • 30 g of the obtained niobium powder was charged and thereinto, nitrogen was continuously introduced at 300°C for 0.5 to 3 hours to obtain niobium nitrides.
  • the nitrogen amount of each nitride was determined using a nitrogen amount measuring apparatus manufactured by LECO which determines the nitrogen amount from the thermal conductivity.
  • the ratio of the measured value to the separately measured mass of powder was designated as the nitrided amount, as a result, the nitrided amount here was from 0.03 to 0.28% by mass.
  • Each niobium nitride was granulated, molded and sintered in the same manner as in Example 94 to obtain a sintered body.
  • the thus-obtained 50 units of sintered bodies each was electrochemically formed using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 200 minutes to form an oxide dielectric film on the surface. Thereafter, an operation of contacting the oxide dielectric film with an equivalent-mass mixed solution of an aqueous 10% ammonium persulfate solution and an aqueous 0.5% anthraquinone sulfonic acid solution and then with a pyrrole vapor was repeated at least 5 times, whereby the other electrode (counter electrode) comprising polypyrrole was formed on the oxide dielectric film. On this counter electrode, a carbon layer and a silver paste layer were stacked in this order.
  • the device as a whole was molded with an epoxy resin to manufacture a chip-type capacitor.
  • the LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute. TABLE 22 Nitrogen Content (wt%) Capacitance.
  • a lanthanum-containing niobium ingot (alloy) having a lanthanum content of 1 mol% was produced by arc melting.
  • an SUS 304-made reactor 50 g of the obtained ingot was placed and hydrogen was continuously introduced thereinto at 400°C for 10 hours. After cooling, the hydrogenated lanthanum-containing niobium cake was placed in an SUS 304-made pot containing SUS-made balls and pulverized for 10 hours.
  • this hydride was formed into a 20 vol% slurry with water, charged together with zirconia balls into an SUS 304-made spike mill; and wet-pulverized for 7 hours.
  • the resulting slurry was subjected to centrifugal sedimentation and decanted to obtain a pulverized product.
  • the pulverized product was dried under reduced pressure in the conditions of 1.33 ⁇ 10 2 Pa and 50°C.
  • the hydrogenated lanthanum-containing niobium powder was dehydrogenated under heating at 1.33 ⁇ 10 -2 Pa and 400°C for 1 hour.
  • the produced lanthanum-containing niobium powder had a mean particle size of 1.0 ⁇ m and the lanthanum content thereof was 1 mol%.
  • the thus-obtained lanthanum-containing niobium powder was granulated under reduced pressure of 4 ⁇ 10 -3 Pa at 1,100°C. Thereafter, the granulated cake was pulverized to obtain a granulated powder having a mean particle size of 100 ⁇ m.
  • the thus-obtained lanthanum-containing niobium granulated powder was molded together with a 0.3-mm ⁇ niobium lead wire to manufacture a molded article having a size of approximately 0.3x0.18x0.45 cm (weighing about 0.1 g).
  • This molded article was allowed to stand under reduced pressure of 4 ⁇ 10 -3 Pa at 1,200°C for 30 minutes and thereby, a sintered body was obtained.
  • the sintered body obtained was electrochemically formed in an aqueous 0.1% phosphoric acid solution at a temperature of 80°C for 200 minutes by applying a voltage of 20 V to form a dielectric layer on the surface. Thereafter, the capacitance in 30% sulfuric acid and the leakage current (hereinafter simply referred to as "LC") in an aqueous 20% phosphoric acid solution were measured. The results obtained are shown in Table 23 (No.1 and No.2).
  • a niobium sintered body comprising at least one element of rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, sulfur, selenium and tellurium, a powder of rubidium; cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium,
  • niobium powder containing at least one element selected from the group consisting of rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, sulfur, selenium and tellurium, sintered bodies were manufactured and each was measured on the capacitance and LC. The results obtained are shown in Table 23(No.1 ,and No.2).
  • niobium powder not containing any of rubidium, cesium, magnesium, strontium, barium, scandium, yttrium, lanthanum, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, vanadium, osmium, iridium, platinum, gold, cadmium, mercury, lead, sulfur, selenium and tellurium and having a different mean particle size were produced in the same manner as in Example 154.
  • lanthanum-containing niobium ingots having a lanthanum content of 0.01 to 20 mol% were produced by varying the amounts of niobium and lanthanum processed by the arc melting. Thereafter, using 500 g of each of the lanthanum-containing niobium ingots having respective lanthanum concentrations, sintered bodies were manufactured by the same operation as in Example 154 and each was measured on the capacitance and LC. The results obtained are shown in Table 24. TABLE 24 Lanthanum Content (mol%) Mean Particle Size ( ⁇ m) Sintering Temp.
  • Example 38 0.00 1.0 1200 87000 424
  • Example 196 0.01 1.0 1200 95000 65
  • Example 197 0.1 1.0 1200 106000 33
  • Example 154 1 1.0 1200 108000 21
  • Example 198 2 1.0 1200 110000 23
  • Example 199 3 1.0 1200 109000 23
  • Example 200 7 1.0 1200 109000 30
  • Example 201 11 1.0 1200 85000 59
  • Example 202 20 1.0 1200 79000 66
  • the hydrogenated niobium powder was dehydrogenated under heating at 1.3 ⁇ 10 -2 Pa and 400°C for 1 hour.
  • the manufactured niobium powder had a mean particle size of 1.0 ⁇ m.
  • any one of lanthanum oxide, lanthanum oxalate, hydrogenated lanthanum, lanthanum nitrate and lanthanum (metal) each having a mean particle size of about 1 ⁇ m was mixed at an arbitrary ratio.
  • the obtained lanthanum-containing niobium powder was granulated under reduced pressure of 4 ⁇ 10 -3 Pa at 1,050°C.
  • the granulated cake was pulverized to obtain a granulated powder having a mean particle size of 90 ⁇ m.
  • the thus-obtained lanthanum-containing niobium granulated powder was molded together with a 0.3-mm ⁇ niobium wire to manufacture a molded article having a size of approximately 0.3x0.18x0.45 cm (weighing about 0.1g). Subsequently, these molded articles were allowed to stand under reduced pressure of 4 ⁇ 10 -3 Pa at 1,250°C for 30 minutes to obtain sintered bodies.
  • the resulting sintered bodies each was electrochemically formed in an aqueous 0.1% phosphoric acid solution at a temperature of 80°C for 200 minutes by applying a voltage of 20 V to form a dielectric layer on the surface. Thereafter, the capacitance in 30% sulfuric acid and the LC in an aqueous 20% phosphoric acid solution were measured. The results obtained are shown in Table 25.
  • lanthanum-containing niobium nitride 10 g of lanthanum-containing niobium powder containing 0.9 mol% of lanthanum and having a mean particle size of 0.9 ⁇ m was manufactured in the same manner as in Example 154 and charged into an SUS 304-made reactor and thereinto, nitrogen was continuously introduced at 300°C for 0.5 to 20 hours to obtain lanthanum-containing niobium nitrides.
  • the nitrogen amount of each nitride was determined using a nitrogen amount measuring apparatus manufactured by LECO which determines the nitrogen amount from the thermal conductivity.
  • the ratio of the measured value to the separately measured mass of powder was designated as the nitrided amount.
  • the nitrided amount here was from 0.02 to 0.81% by mass.
  • Example 154 The thus-obtained lanthanum-containing niobium nitrides each was granulated, molded and sintered in the same manner as in Example 154 and each sintered body obtained was electrochemically formed in an aqueous 0.1% phosphoric acid solution at a temperature of 80°C for 200 minutes by applying a voltage of 20 V to form a dielectric layer on the surface. Thereafter, the capacitance in 30% sulfuric acid and the LC value in an aqueous 20% phosphoric acid solution were measured. The results obtained are shown in Table 26.
  • Example 208 0.9 0.02 120000 29
  • Example 209 0.9 0.12 122000 19
  • Example 210 0.9 0.26 121000 19
  • Example 211 0.9 0.45 124000 23
  • Example 212 0.9 0.81 120000 24
  • a lanthanum-containing niobium powder containing 10 mol% of lanthanum and having a mean particle size of 1.0 ⁇ m was obtained in the same manner as in Example 154.
  • niobium powder had a mean particle size of 1.2 ⁇ m.
  • the thus-obtained lanthanum-containing niobium powder was thoroughly mixed with niobium powder at a ratio shown in Table 27 and the resulting mixtures each was granulated, molded and sintered in the same manner as in Example 154 to obtain sintered bodies.
  • the capacitance and the LC value of each sintered body were measured and the results obtained are shown in Table 27.
  • lanthanum-containing niobium powder containing 10 mol% of lanthanum and having a mean particle size of 1.0 ⁇ m was obtained in the same manner as in Example 1.
  • 50 g of a niobium ingot was placed in an SUS 304-made reactor and hydrogen was continuously introduced thereinto at 400°C for 12 hours. After cooling, the hydrogenated niobium cake was placed in an SUS 304-made pot containing iron-made balls and pulverized for 10 hours.
  • This pulverized product was charged into the same SUS 304-made reactor as above and again hydrogenated under the above-described conditions. Thereafter, this hydride was formed into a 20 vol% slurry with water, charged together with zirconia balls into an SUS 304-made spike mill, and wet-pulverized for 6 hours:
  • the resulting slurry was subjected to centrifugal sedimentation and decanted to obtain a pulverized product.
  • the pulverized product was dried under reduced pressure in the conditions of 1.3 ⁇ 10 2 Pa and 50°C. Subsequently, the hydrogenated niobium powder was dehydrogenated under heating under reduced pressure of 1.33 ⁇ 10 -2 Pa at 400°C for 1 hour.
  • the manufactured niobium powder had a mean particle size of 1.1 ⁇ m.
  • the thus-obtained lanthanum-containing niobium powder was thoroughly mixed with niobium powder at an arbitrary ratio and after obtaining nitrides in the same manner as in Example 210, the nitrides each was granulated, molded and sintered to obtain sintered bodies. The capacitance and the LC value of each sintered body were measured and the results obtained are shown in Table 27.
  • Example 219 and Example 220 50 Units of sintered bodies were prepared in each of Example 219 and Example 220 in same manner as in Example 154 and Example 182, respectively. These sintered bodies each was electrochemically oxidized using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 6 hours to form an oxide dielectric film on the surface. Subsequently, an operation of dipping each sintered body in an aqueous 60% manganese nitrate solution and then heating it at 220°C for 30 minutes was repeated to form a manganese dioxide layer as the other electrode (counter electrode) layer on the oxide dielectric film. On this counter electrode layer, a carbon layer and a silver paste layer were stacked in this order.
  • the device as a whole was molded with an epoxy resin to manufacture a chip-type capacitor.
  • the LC value is a value measured at room temperature by applying a voltage of 6.3V for 1 minute.
  • Example 221 and Example 222 50 Units of sintered bodies were prepared in each of Example 221 and Example 222 in same manner as in Example 159 and Example 204, respectively. These sintered bodies each was electrochemically oxidized using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 6 hours to form an oxide dielectric film on the surface. Subsequently, an operation of dipping each sintered body in a mixed solution of an aqueous 35% lead acetate solution and an aqueous 35% ammonium persulfate solution (1:1 by volume) and then allowing the reaction to proceed at 40°C for 1 hour was repeated to form a mixed layer of lead dioxide and lead sulfate as the other electrode (counter electrode) layer on the oxide dielectric film.
  • the LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.
  • Example 223, Example 224, Example 225 and Example 226 50 Units of sintered bodies were prepared in each of Example 223, Example 224, Example 225 and Example 226 in same manner as in Example 167, Example 189, Example 211 and Example 215, respectively.
  • These sintered bodies each was electrochemically oxidized using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 6 hours to form an oxide dielectric film on the surface.
  • an operation of contacting the oxide dielectric film with an equivalent-mass mixed solution of an aqueous 10% ammonium persulfate solution and an aqueous 0.5% anthraquinonesulfonic acid solution and then with a pyrrole vapor was repeated at least 5 times, whereby the other electrode (counter electrode) comprising polypyrrole was formed on the oxide dielectric film.
  • the LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.
  • Example 227 50 Units of sintered bodies were prepared in each of Example 227, Example 228, Example 229, Example 230 and Example 231 in same manner as in Example 170, Example 191, Example 205, Example 210 and Example 218, respectively.
  • These sintered bodies each was electrochemically oxidized using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 6 hours to form an oxide dielectric film on the surface.
  • the niobium sintered body was dipped into an aqueous solution containing 25% by mass of ammonium persulfate (Solution 1), then pulled up and dried at 80°C for 30 minutes.
  • Solution 1 ammonium persulfate
  • the sintered body having formed thereon a dielectric material was dipped in an isopropanol solution containing 18% by mass of 3,4-ethylenedioxythiophene (Solution 2), then pulled up and left standing in an atmosphere of 60°C for 10 minutes to allow the oxidation-polymerization to proceed.
  • the resulting sintered body was again dipped in Solution 1 and then treated in the same manner as above. The operation from the dipping in Solution 1 until the oxidation polymerization was repeated 8 times.
  • the sintered body was washed with hot water at 50°C for 10 minutes and dried at 100°C for 30 minutes, whereby the other electrode (counter electrode) comprising electrically conducting poly(3,4-ethylenedioxythiophene) was formed.
  • the LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.
  • the manufactured niobium powder had a mean particle size of 1.3 ⁇ m.
  • 30 g of the thus-obtained niobium powder was charged and thereinto, nitrogen was continuously introduced at 300°C for 0.5 to 4 hours to obtain niobium nitrides.
  • the nitrogen amount of each nitride was determined using the nitrogen amount measuring apparatus manufactured by LECO which determines the nitrogen amount from the thermal conductivity.
  • the ratio of the measured value to the separately measured mass of powder was designated as the nitrided amount, as a result, the nitrided amount here was from 0.02 to 0.30% by mass.
  • Each niobium nitride was granulated, molded and sintered in the same manner as in Example 154 to obtain a sintered body.
  • the thus-obtained 50 units of sintered bodies each was electrochemically oxidized using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 6 hours to form an oxide dielectric film on the surface.
  • the resulting slurry was subjected to centrifugal sedimentation and decanted to obtain a pulverized product.
  • the pulverized product was dried under reduced pressure of 1.33 ⁇ 10 2 Pa at 50°C.
  • the hydrogenated niobium powder was dehydrogenated under heating under reduced pressure of 1.33 ⁇ 10 -2 Pa at 400°C for 1 hour.
  • the manufactured niobium powder had a mean particle size of 1.0 ⁇ m.
  • 30 g of the obtained niobium powder was charged and thereinto, nitrogen was continuously introduced at 300°C for 0.5 to 3 hours to obtain niobium nitrides.
  • the nitrogen amount of each nitride was determined using a nitrogen amount measuring apparatus manufactured by LECO which determines the nitrogen amount from the thermal conductivity.
  • the ratio of the measured value to the separately measured mass of powder was designated as the nitrided amount, as a result, the nitrided amount here was from 0.03 to 0.28% by mass.
  • Each niobium nitride was granulated, molded and sintered in the same manner as in Example 154 to obtain a sintered body.
  • the thus-obtained 50 units of sintered bodies each was electrochemically oxidized using an aqueous 0.1% phosphoric acid solution at a voltage of 20 V for 6 hours to form an oxide dielectric film on the surface.
  • the LC value is a value measured at room temperature by applying a voltage of 6.3 V for 1 minute.
  • Example 219 - 486 15 0/50 Example 220 - 471 20 0/50
  • Example 221 - 482 16 0/50 Example 222 - 504 17 0/50
  • Example 225 0.45 546 16 0/50
  • Example 228 - 937 119 0/50
  • Example 229 - 509 15 0/50 Example 230 0.26 532 12 0/50
  • Example 231 - 491 13 0/50 Comparative Example 40 0.02 398 47 4/50 Comparative Example 41
  • Example 46 Nb/MnO 2 Comp.
  • Example 40 47/277 5.9 times 50/50 Comp.
  • Example 47 Nb/MnO 2 Comp.
  • Example 42 40/208 5.2 times 50/50 Comp.
  • Example 48 Nb/Polypyrrole Comp.
  • Example 45 41/209 5.1 times 50/50 *1
  • a sintered body used was obtained by the same method as in Example 101, and a chip type capacitor was produced by the same method as in Example 148.

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WO2002015208A1 (fr) 2002-02-21
BR122015027076B1 (pt) 2017-02-21
CN100477040C (zh) 2009-04-08
KR100758945B1 (ko) 2007-09-14
AU2001277734B2 (en) 2007-01-04
BR0113215A (pt) 2005-02-01
EP1324359B1 (de) 2013-01-02
JP4562986B2 (ja) 2010-10-13
AU2007200912B2 (en) 2009-01-22
KR20060006104A (ko) 2006-01-18
EP1324359A1 (de) 2003-07-02
EP1324359B2 (de) 2017-10-04
CA2418865A1 (en) 2002-02-21
KR20060114391A (ko) 2006-11-06
EP2224462A3 (de) 2011-03-09
KR100759290B1 (ko) 2007-09-17
CN1446364A (zh) 2003-10-01
EP2221840B1 (de) 2013-10-09
EP2221839B1 (de) 2013-10-09
AU7773401A (en) 2002-02-25

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